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QString Class Reference
[QtCore module]

The QString class provides a Unicode character string. More...

Types

Methods

Static Methods

Special Methods

Detailed Description

This class can be pickled.

A Python string or unicode object, a QLatin1String or a QChar may be used whenever a QString is expected.

The QString class provides a Unicode character string.

QString stores a string of 16-bit QChars, where each QChar corresponds one Unicode 4.0 character. (Unicode characters with code values above 65535 are stored using surrogate pairs, i.e., two consecutive QChars.)

Unicode is an international standard that supports most of the writing systems in use today. It is a superset of US-ASCII (ANSI X3.4-1986) and Latin-1 (ISO 8859-1), and all the US-ASCII/Latin-1 characters are available at the same code positions.

Behind the scenes, QString uses implicit sharing (copy-on-write) to reduce memory usage and to avoid the needless copying of data. This also helps reduce the inherent overhead of storing 16-bit characters instead of 8-bit characters.

In addition to QString, Qt also provides the QByteArray class to store raw bytes and traditional 8-bit '\0'-terminated strings. For most purposes, QString is the class you want to use. It is used throughout the Qt API, and the Unicode support ensures that your applications will be easy to translate if you want to expand your application's market at some point. The two main cases where QByteArray is appropriate are when you need to store raw binary data, and when memory conservation is critical (e.g., with Qt for Embedded Linux).

Initializing a String

One way to initialize a QString is simply to pass a const char * to its constructor. For example, the following code creates a QString of size 5 containing the data "Hello":

 QString str = "Hello";

QString converts the const char * data into Unicode using the fromAscii() function. By default, fromAscii() treats character above 128 as Latin-1 characters, but this can be changed by calling QTextCodec.setCodecForCStrings().

In all of the QString functions that take const char * parameters, the const char * is interpreted as a classic C-style '\0'-terminated string. It is legal for the const char * parameter to be 0.

You can also provide string data as an array of QChars:

 static const QChar data[4] = { 0x0055, 0x006e, 0x10e3, 0x03a3 };
 QString str(data, 4);

QString makes a deep copy of the QChar data, so you can modify it later without experiencing side effects. (If for performance reasons you don't want to take a deep copy of the character data, use QString.fromRawData() instead.)

Another approach is to set the size of the string using resize() and to initialize the data character per character. QString uses 0-based indexes, just like C++ arrays. To access the character at a particular index position, you can use operator[](). On non-const strings, operator[]() returns a reference to a character that can be used on the left side of an assignment. For example:

 QString str;
 str.resize(4);

 str[0] = QChar('U');
 str[1] = QChar('n');
 str[2] = QChar(0x10e3);
 str[3] = QChar(0x03a3);

For read-only access, an alternative syntax is to use the at() function:

 QString str;

 for (int i = 0; i < str.size(); ++i) {
     if (str.at(i) >= QChar('a') && str.at(i) <= QChar('f'))
         qDebug() << "Found character in range [a-f]";
 }

The at() function can be faster than operator[](), because it never causes a deep copy to occur. Alternatively, use the left(), right(), or mid() functions to extract several characters at a time.

A QString can embed '\0' characters (QChar.Null). The size() function always returns the size of the whole string, including embedded '\0' characters.

After a call to the resize() function, newly allocated characters have undefined values. To set all the characters in the string to a particular value, use the fill() function.

QString provides dozens of overloads designed to simplify string usage. For example, if you want to compare a QString with a string literal, you can write code like this and it will work as expected:

 QString str;

 if (str == "auto" || str == "extern"
         || str == "static" || str == "register") {
     // ...
 }

You can also pass string literals to functions that take QStrings as arguments, invoking the QString(const char *) constructor. Similarly, you can pass a QString to a function that takes a const char * argument using the qPrintable() macro which returns the given QString as a const char *. This is equivalent to calling <QString>.toLocal8Bit().constData().

Manipulating String Data

QString provides the following basic functions for modifying the character data: append(), prepend(), insert(), replace(), and remove(). For example:

 QString str = "and";
 str.prepend("rock ");     // str == "rock and"
 str.append(" roll");        // str == "rock and roll"
 str.replace(5, 3, "&");   // str == "rock & roll"

If you are building a QString gradually and know in advance approximately how many characters the QString will contain, you can call reserve(), asking QString to preallocate a certain amount of memory. You can also call capacity() to find out how much memory QString actually allocated.

The replace() and remove() functions' first two arguments are the position from which to start erasing and the number of characters that should be erased. If you want to replace all occurrences of a particular substring with another, use one of the two-parameter replace() overloads.

A frequent requirement is to remove whitespace characters from a string ('\n', '\t', ' ', etc.). If you want to remove whitespace from both ends of a QString, use the trimmed() function. If you want to remove whitespace from both ends and replace multiple consecutive whitespaces with a single space character within the string, use simplified().

If you want to find all occurrences of a particular character or substring in a QString, use the indexOf() or lastIndexOf() functions. The former searches forward starting from a given index position, the latter searches backward. Both return the index position of the character or substring if they find it; otherwise, they return -1. For example, here's a typical loop that finds all occurrences of a particular substring:

 QString str = "We must be <b>bold</b>, very <b>bold</b>";
 int j = 0;

 while ((j = str.indexOf("<b>", j)) != -1) {
     qDebug() << "Found <b> tag at index position" << j;
     ++j;
 }

QString provides many functions for converting numbers into strings and strings into numbers. See the arg() functions, the setNum() functions, the number() static functions, and the toInt(), toDouble(), and similar functions.

To get an upper- or lowercase version of a string use toUpper() or toLower().

Lists of strings are handled by the QStringList class. You can split a string into a list of strings using the split() function, and join a list of strings into a single string with an optional separator using QStringList.join(). You can obtain a list of strings from a string list that contain a particular substring or that match a particular QRegExp using the QStringList.filter() function.

Querying String Data

If you want to see if a QString starts or ends with a particular substring use startsWith() or endsWith(). If you simply want to check whether a QString contains a particular character or substring, use the contains() function. If you want to find out how many times a particular character or substring occurs in the string, use count().

QStrings can be compared using overloaded operators such as operator<(), operator<=(), operator==(), operator>=(), and so on. Note that the comparison is based exclusively on the numeric Unicode values of the characters. It is very fast, but is not what a human would expect; the QString.localeAwareCompare() function is a better choice for sorting user-interface strings.

To obtain a pointer to the actual character data, call data() or constData(). These functions return a pointer to the beginning of the QChar data. The pointer is guaranteed to remain valid until a non-const function is called on the QString.

Converting Between 8-Bit Strings and Unicode Strings

QString provides the following four functions that return a const char * version of the string as QByteArray: toAscii(), toLatin1(), toUtf8(), and toLocal8Bit().

To convert from one of these encodings, QString provides fromAscii(), fromLatin1(), fromUtf8(), and fromLocal8Bit(). Other encodings are supported through the QTextCodec class.

As mentioned above, QString provides a lot of functions and operators that make it easy to interoperate with const char * strings. But this functionality is a double-edged sword: It makes QString more convenient to use if all strings are US-ASCII or Latin-1, but there is always the risk that an implicit conversion from or to const char * is done using the wrong 8-bit encoding. To minimize these risks, you can turn off these implicit conversions by defining the following two preprocessor symbols:

One way to define these preprocessor symbols globally for your application is to add the following entry to your qmake project file:

 DEFINES += QT_NO_CAST_FROM_ASCII \
            QT_NO_CAST_TO_ASCII

You then need to explicitly call fromAscii(), fromLatin1(), fromUtf8(), or fromLocal8Bit() to construct a QString from an 8-bit string, or use the lightweight QLatin1String class, for example:

 QString url = QLatin1String("http://www.unicode.org/");

Similarly, you must call toAscii(), toLatin1(), toUtf8(), or toLocal8Bit() explicitly to convert the QString to an 8-bit string. (Other encodings are supported through the QTextCodec class.)

Note for C Programmers
Due to C++'s type system and the fact that QString is implicitly shared, QStrings may be treated like ints or other basic types. For example: 
 QString Widget.boolToString(bool b)
 {
     QString result;
     if (b)
         result = "True";
     else
         result = "False";
     return result;
 }

The result variable, is a normal variable allocated on the stack. When return is called, and because we're returning by value, the copy constructor is called and a copy of the string is returned. No actual copying takes place thanks to the implicit sharing.

Distinction Between Null and Empty Strings

For historical reasons, QString distinguishes between a null string and an empty string. A null string is a string that is initialized using QString's default constructor or by passing (const char *)0 to the constructor. An empty string is any string with size 0. A null string is always empty, but an empty string isn't necessarily null:

 QString().isNull();               // returns true
 QString().isEmpty();              // returns true

 QString("").isNull();             // returns false
 QString("").isEmpty();            // returns true

 QString("abc").isNull();          // returns false
 QString("abc").isEmpty();         // returns false

All functions except isNull() treat null strings the same as empty strings. For example, toAscii().constData() returns a pointer to a '\0' character for a null string (not a null pointer), and QString() compares equal to QString(""). We recommend that you always use the isEmpty() function and avoid isNull().

Argument Formats

In member functions where an argument format can be specified (e.g., arg(), number()), the argument format can be one of the following:

Format Meaning
e format as [-]9.9e[+|-]999
E format as [-]9.9E[+|-]999
f format as [-]9.9
g use e or f format, whichever is the most concise
G use E or f format, whichever is the most concise

A precision is also specified with the argument format. For the 'e', 'E', and 'f' formats, the precision represents the number of digits after the decimal point. For the 'g' and 'G' formats, the precision represents the maximum number of significant digits (trailing zeroes are omitted).

More Efficient String Construction

Using the QString '+' operator, it is easy to construct a complex string from multiple substrings. You will often write code like this:

     QString foo;
     QString type = "long";

     foo->setText(QLatin1String("vector<") + type + QLatin1String(">.iterator"));

     if (foo.startsWith("(" + type + ") 0x"))
         ...

There is nothing wrong with either of these string constructions, but there are a few hidden inefficiencies. Beginning with Qt 4.6, you can eliminate them.

First, multiple uses of the '+' operator usually means multiple memory allocations. When concatenating n substrings, where n > 2, there can be as many as n - 1 calls to the memory allocator.

Second, QLatin1String does not store its length internally but calls qstrlen() when it needs to know its length.

In 4.6, an internal template class QStringBuilder has been added along with a few helper functions. This class is marked internal and does not appear in the documentation, because you aren't meant to instantiate it in your code. Its use will be automatic, as described below. The class is found in src/corelib/tools/qstringbuilder.cpp if you want to have a look at it.

QStringBuilder uses expression templates and reimplements the '%' operator so that when you use '%' for string concatenation instead of '+', multiple substring concatenations will be postponed until the final result is about to be assigned to a QString. At this point, the amount of memory required for the final result is known. The memory allocator is then called once to get the required space, and the substrings are copied into it one by one.

QLatin1Literal is a second internal class that can replace QLatin1String, which can't be changed for compatibility reasons. QLatin1Literal stores its length, thereby saving time when QStringBuilder computes the amount of memory required for the final string.

Additional efficiency is gained by inlining and reduced reference counting (the QString created from a QStringBuilder typically has a ref count of 1, whereas QString.append() needs an extra test).

There are three ways you can access this improved method of string construction. The straightforward way is to include QStringBuilder wherever you want to use it, and use the '%' operator instead of '+' when concatenating strings:

     #include <QStringBuilder>

     QString hello("hello");
     QStringRef el(&hello, 2, 3);
     QLatin1String world("world");
     QString message =  hello % el % world % QChar('!');

A more global approach which is the most convenient but not entirely source compatible, is to this define in your .pro file:

     DEFINES *= QT_USE_QSTRINGBUILDER

and the '+' will automatically be performed as the QStringBuilder '%' everywhere.

Type Documentation

QString.NormalizationForm

This enum describes the various normalized forms of Unicode text.

Constant Value Description
QString.NormalizationForm_D 0 Canonical Decomposition
QString.NormalizationForm_C 1 Canonical Decomposition followed by Canonical Composition
QString.NormalizationForm_KD 2 Compatibility Decomposition
QString.NormalizationForm_KC 3 Compatibility Decomposition followed by Canonical Composition

See also normalized() and Unicode Standard Annex #15.

QString.SectionFlag

This enum specifies flags that can be used to affect various aspects of the section() function's behavior with respect to separators and empty fields.

Constant Value Description
QString.SectionDefault 0x00 Empty fields are counted, leading and trailing separators are not included, and the separator is compared case sensitively.
QString.SectionSkipEmpty 0x01 Treat empty fields as if they don't exist, i.e. they are not considered as far as start and end are concerned.
QString.SectionIncludeLeadingSep 0x02 Include the leading separator (if any) in the result string.
QString.SectionIncludeTrailingSep 0x04 Include the trailing separator (if any) in the result string.
QString.SectionCaseInsensitiveSeps 0x08 Compare the separator case-insensitively.

The SectionFlags type is a typedef for QFlags<SectionFlag>. It stores an OR combination of SectionFlag values.

See also section().

QString.SplitBehavior

This enum specifies how the split() function should behave with respect to empty strings.

Constant Value Description
QString.KeepEmptyParts 0 If a field is empty, keep it in the result.
QString.SkipEmptyParts 1 If a field is empty, don't include it in the result.

See also split().

Method Documentation

QString.__init__ (self)

Constructs a null string. Null strings are also empty.

See also isEmpty().

QString.__init__ (self, QKeySequence)

This method is only available if the QtGui module is imported.

Constructs a null string. Null strings are also empty.

See also isEmpty().

QString.__init__ (self, QScriptString)

This method is only available if the QtScript module is imported.

Constructs a null string. Null strings are also empty.

See also isEmpty().

QString.__init__ (self, int size, QChar c)

Constructs a string initialized with the first size characters of the QChar array unicode.

QString makes a deep copy of the string data. The unicode data is copied as is and the Byte Order Mark is preserved if present.

QString.__init__ (self, QString s)

Constructs a string initialized with the characters of the QChar array unicode, which must be terminated with a 0.

QString makes a deep copy of the string data. The unicode data is copied as is and the Byte Order Mark is preserved if present.

This function was introduced in Qt 4.7.

QString.__init__ (self, QByteArray a)

Constructs a string of size 1 containing the character ch.

QString.__init__ (self, QUuid)

Constructs a string of the given size with every character set to ch.

See also fill().

QString QString.append (self, QString s)

Appends the string str onto the end of this string.

Example:

 QString x = "free";
 QString y = "dom";

 x.append(y);
 // x == "freedom"

This is the same as using the insert() function:

 x.insert(x.size(), y);

The append() function is typically very fast (constant time), because QString preallocates extra space at the end of the string data so it can grow without reallocating the entire string each time.

See also operator+=(), prepend(), and insert().

QString QString.append (self, QLatin1String s)

Appends the given string reference to this string and returns the result.

This function was introduced in Qt 4.4.

QString QString.append (self, QByteArray s)

This function overloads append().

Appends the Latin-1 string str to this string.

QString QString.arg (self, int a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' '))

Returns a copy of this string with the lowest numbered place marker replaced by string a, i.e., %1, %2, ..., %99.

fieldWidth specifies the minimum amount of space that argument a shall occupy. If a requires less space than fieldWidth, it is padded to fieldWidth with character fillChar. A positive fieldWidth produces right-aligned text. A negative fieldWidth produces left-aligned text.

This example shows how we might create a status string for reporting progress while processing a list of files:

 QString i;           // current file's number
 QString total;       // number of files to process
 QString fileName;    // current file's name

 QString status = QString("Processing file %1 of %2: %3")
                 .arg(i).arg(total).arg(fileName);

First, arg(i) replaces %1. Then arg(total) replaces %2. Finally, arg(fileName) replaces %3.

One advantage of using arg() over sprintf() is that the order of the numbered place markers can change, if the application's strings are translated into other languages, but each arg() will still replace the lowest numbered unreplaced place marker, no matter where it appears. Also, if place marker %i appears more than once in the string, the arg() replaces all of them.

If there is no unreplaced place marker remaining, a warning message is output and the result is undefined. Place marker numbers must be in the range 1 to 99.

QString QString.arg (self, float a, int fieldWidth = 0, str format = 'g', int precision = -1, QChar fillChar = QLatin1Char(' '))

This function overloads arg().

This is the same as str.arg(a1).arg(a2), except that the strings a1 and a2 are replaced in one pass. This can make a difference if a1 contains e.g. %1:

 QString str;
 str = "%1 %2";

 str.arg("%1f", "Hello");        // returns "%1f Hello"
 str.arg("%1f").arg("Hello");    // returns "Hellof %2"

QString QString.arg (self, int a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' '))

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3), except that the strings a1, a2 and a3 are replaced in one pass.

QString QString.arg (self, int a, int fieldWidth = 0, int base = 10, QChar fillChar = QLatin1Char(' '))

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4), except that the strings a1, a2, a3 and a4 are replaced in one pass.

QString QString.arg (self, QString a, int fieldWidth = 0, QChar fillChar = QLatin1Char(' '))

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5), except that the strings a1, a2, a3, a4, and a5 are replaced in one pass.

QString QString.arg (self, QString a1, QString a2)

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6)), except that the strings a1, a2, a3, a4, a5, and a6 are replaced in one pass.

QString QString.arg (self, QString a1, QString a2, QString a3)

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7), except that the strings a1, a2, a3, a4, a5, a6, and a7 are replaced in one pass.

QString QString.arg (self, QString a1, QString a2, QString a3, QString a4)

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8), except that the strings a1, a2, a3, a4, a5, a6, a7, and a8 are replaced in one pass.

QString QString.arg (self, QString a1, QString a2, QString a3, QString a4, QString a5)

This function overloads arg().

This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8).arg(a9), except that the strings a1, a2, a3, a4, a5, a6, a7, a8, and a9 are replaced in one pass.

QString QString.arg (self, QString a1, QString a2, QString a3, QString a4, QString a5, QString a6)

This function overloads arg().

The a argument is expressed in base base, which is 10 by default and must be between 2 and 36. For bases other than 10, a is treated as an unsigned integer.

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale, set by QLocale.setDefault(). If no default locale was specified, the "C" locale is used. The 'L' flag is ignored if base is not 10.

 QString str;
 str = QString("Decimal 63 is %1 in hexadecimal")
         .arg(63, 0, 16);
 // str == "Decimal 63 is 3f in hexadecimal"

 QLocale.setDefault(QLocale(QLocale.English, QLocale.UnitedStates));
 str = QString("%1 %L2 %L3")
         .arg(12345)
         .arg(12345)
         .arg(12345, 0, 16);
 // str == "12345 12,345 3039"

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString.arg (self, QString a1, QString a2, QString a3, QString a4, QString a5, QString a6, QString a7)

This function overloads arg().

The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString.arg (self, QString a1, QString a2, QString a3, QString a4, QString a5, QString a6, QString a7, QString a8)

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The a argument is expressed in the given base, which is 10 by default and must be between 2 and 36.

The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale. The default locale is determined from the system's locale settings at application startup. It can be changed using QLocale.setDefault(). The 'L' flag is ignored if base is not 10.

 QString str;
 str = QString("Decimal 63 is %1 in hexadecimal")
         .arg(63, 0, 16);
 // str == "Decimal 63 is 3f in hexadecimal"

 QLocale.setDefault(QLocale(QLocale.English, QLocale.UnitedStates));
 str = QString("%1 %L2 %L3")
         .arg(12345)
         .arg(12345)
         .arg(12345, 0, 16);
 // str == "12345 12,345 3039"

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QString QString.arg (self, QString a1, QString a2, QString a3, QString a4, QString a5, QString a6, QString a7, QString a8, QString a9)

This function overloads arg().

fieldWidth specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value produces right-aligned text; a negative value produces left-aligned text.

The base argument specifies the base to use when converting the integer a to a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.

If fillChar is '0' (the number 0, ASCII 48), the locale's zero is used. For negative numbers, zero padding might appear before the minus sign.

QChar QString.at (self, int i)

Returns the character at the given index position in the string.

The position must be a valid index position in the string (i.e., 0 <= position < size()).

See also operator[]().

int QString.capacity (self)

Returns the maximum number of characters that can be stored in the string without forcing a reallocation.

The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to know how many characters are in the string, call size().

See also reserve() and squeeze().

QString.chop (self, int n)

Removes n characters from the end of the string.

If n is greater than size(), the result is an empty string.

Example:

 QString str("LOGOUT\r\n");
 str.chop(2);
 // str == "LOGOUT"

If you want to remove characters from the beginning of the string, use remove() instead.

See also truncate(), resize(), and remove().

QString.clear (self)

Clears the contents of the string and makes it empty.

See also resize() and isEmpty().

int QString.compare (self, QString s)

Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.

If cs is Qt.CaseSensitive, the comparison is case sensitive; otherwise the comparison is case insensitive.

Case sensitive comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-visible strings with localeAwareCompare().

 int x = QString.compare("aUtO", "AuTo", Qt.CaseInsensitive);  // x == 0
 int y = QString.compare("auto", "Car", Qt.CaseSensitive);     // y > 0
 int z = QString.compare("auto", "Car", Qt.CaseInsensitive);   // z < 0

This function was introduced in Qt 4.2.

See also operator==(), operator<(), and operator>().

int QString.compare (self, QString s, Qt.CaseSensitivity cs)

This function overloads compare().

Performs a case sensitive compare of s1 and s2.

int QString.compare (self, QLatin1String other, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads compare().

Performs a comparison of s1 and s2, using the case sensitivity setting cs.

This function was introduced in Qt 4.2.

int QString.compare (self, QStringRef ref, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads compare().

Performs a comparison of s1 and s2, using the case sensitivity setting cs.

This function was introduced in Qt 4.2.

int QString.compare (QString s1, QString s2)

This function overloads compare().

Lexically compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.

Equivalent to compare(*this, other).

int QString.compare (QString s1, QString s2, Qt.CaseSensitivity cs)

This function overloads compare().

Same as compare(*this, other, cs).

This function was introduced in Qt 4.2.

int QString.compare (QString s1, QLatin1String s2, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads compare().

Same as compare(*this, other, cs).

This function was introduced in Qt 4.2.

int QString.compare (QLatin1String s1, QString s2, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads compare().

Compares the string reference, ref, with the string and returns an integer less than, equal to, or greater than zero if the string is less than, equal to, or greater than ref.

int QString.compare (QString s1, QStringRef s2, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads compare().

bool QString.contains (self, QString str, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Returns true if this string contains an occurrence of the string str; otherwise returns false.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

 QString str = "Peter Pan";
 str.contains("peter", Qt.CaseInsensitive);    // returns true

See also indexOf() and count().

bool QString.contains (self, QStringRef s, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Returns true if this string contains an occurrence of the string reference str; otherwise returns false.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also indexOf() and count().

bool QString.contains (self, QRegExp rx)

int QString.count (self)

Returns the number of (potentially overlapping) occurrences of the string str in this string.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

See also contains() and indexOf().

int QString.count (self, QString str, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads count().

Returns the number of occurrences of character ch in the string.

int QString.count (self, QStringRef str, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads count().

Returns the number of (potentially overlapping) occurrences of the string reference str in this string.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also contains() and indexOf().

int QString.count (self, QRegExp)

This function overloads count().

Returns the number of times the regular expression rx matches in the string.

This function counts overlapping matches, so in the example below, there are four instances of "ana" or "ama":

 QString str = "banana and panama";
 str.count(QRegExp("a[nm]a"));    // returns 4

bool QString.endsWith (self, QString s, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Returns true if the string ends with s; otherwise returns false.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

 QString str = "Bananas";
 str.endsWith("anas");         // returns true
 str.endsWith("pple");         // returns false

See also startsWith().

bool QString.endsWith (self, QStringRef s, Qt.CaseSensitivity cs = Qt.CaseSensitive)

bool QString.endsWith (self, QLatin1String s, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads endsWith().

Returns true if the string ends with the string reference s; otherwise returns false.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also startsWith().

QString QString.fill (self, QChar ch, int size = -1)

Sets every character in the string to character ch. If size is different from -1 (default), the string is resized to size beforehand.

Example:

 QString str = "Berlin";
 str.fill('z');
 // str == "zzzzzz"

 str.fill('A', 2);
 // str == "AA"

See also resize().

QString QString.fromAscii (str str, int size = -1)

Returns a QString initialized with the first size characters from the string str.

If size is -1 (default), it is taken to be qstrlen(str).

Note that, despite the name, this function actually uses the codec defined by QTextCodec.setCodecForCStrings() to convert str to Unicode. Depending on the codec, it may not accept valid US-ASCII (ANSI X3.4-1986) input. If no codec has been set, this function does the same as fromLatin1().

See also toAscii(), fromLatin1(), fromUtf8(), and fromLocal8Bit().

QString QString.fromLatin1 (str str, int size = -1)

Returns a QString initialized with the first size characters of the Latin-1 string str.

If size is -1 (default), it is taken to be qstrlen(str).

See also toLatin1(), fromAscii(), fromUtf8(), and fromLocal8Bit().

QString QString.fromLocal8Bit (str str, int size = -1)

Returns a QString initialized with the first size characters of the 8-bit string str.

If size is -1 (default), it is taken to be qstrlen(str).

QTextCodec.codecForLocale() is used to perform the conversion.

See also toLocal8Bit(), fromAscii(), fromLatin1(), and fromUtf8().

QString QString.fromUtf8 (str str, int size = -1)

Returns a QString initialized with the first size bytes of the UTF-8 string str.

If size is -1 (default), it is taken to be qstrlen(str).

UTF-8 is a Unicode codec and can represent all characters in a Unicode string like QString. However, invalid sequences are possible with UTF-8 and, if any such are found, they will be replaced with one or more "replacement characters", or suppressed. These include non-Unicode sequences, non-characters, overlong sequences or surrogate codepoints encoded into UTF-8.

Non-characters are codepoints that the Unicode standard reserves and must not be used in text interchange. They are the last two codepoints in each Unicode Plane (U+FFFE, U+FFFF, U+1FFFE, U+1FFFF, U+2FFFE, etc.), as well as 16 codepoints in the range U+FDD0..U+FDDF, inclusive.

See also toUtf8(), fromAscii(), fromLatin1(), and fromLocal8Bit().

int QString.indexOf (self, QString str, int from = 0, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

 QString x = "sticky question";
 QString y = "sti";
 x.indexOf(y);               // returns 0
 x.indexOf(y, 1);            // returns 10
 x.indexOf(y, 10);           // returns 10
 x.indexOf(y, 11);           // returns -1

If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

See also lastIndexOf(), contains(), and count().

int QString.indexOf (self, QStringRef str, int from = 0, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

 QString x = "sticky question";
 QString y = "sti";
 x.indexOf(y);               // returns 0
 x.indexOf(y, 1);            // returns 10
 x.indexOf(y, 10);           // returns 10
 x.indexOf(y, 11);           // returns -1

If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

This function was introduced in Qt 4.5.

See also lastIndexOf(), contains(), and count().

int QString.indexOf (self, QLatin1String str, int from = 0, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads indexOf().

Returns the index position of the first occurrence of the character ch in the string, searching forward from index position from. Returns -1 if ch could not be found.

int QString.indexOf (self, QRegExp rx, int from = 0)

This function overloads indexOf().

Returns the index position of the first occurrence of the string reference str in this string, searching forward from index position from. Returns -1 if str is not found.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

QString QString.insert (self, int i, QString s)

Inserts the string str at the given index position and returns a reference to this string.

Example:

 QString str = "Meal";
 str.insert(1, QString("ontr"));
 // str == "Montreal"

If the given position is greater than size(), the array is first extended using resize().

See also append(), prepend(), replace(), and remove().

QString QString.insert (self, int i, QLatin1String s)

This function overloads insert().

Inserts the Latin-1 string str at the given index position.

bool QString.isEmpty (self)

Returns true if the string has no characters; otherwise returns false.

Example:

 QString().isEmpty();            // returns true
 QString("").isEmpty();          // returns true
 QString("x").isEmpty();         // returns false
 QString("abc").isEmpty();       // returns false

See also size().

bool QString.isNull (self)

Returns true if this string is null; otherwise returns false.

Example:

 QString().isNull();             // returns true
 QString("").isNull();           // returns false
 QString("abc").isNull();        // returns false

Qt makes a distinction between null strings and empty strings for historical reasons. For most applications, what matters is whether or not a string contains any data, and this can be determined using the isEmpty() function.

See also isEmpty().

bool QString.isRightToLeft (self)

Returns true if the string is read right to left.

bool QString.isSimpleText (self)

int QString.lastIndexOf (self, QString str, int from = -1, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Returns the index position of the last occurrence of the string str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

 QString x = "crazy azimuths";
 QString y = "az";
 x.lastIndexOf(y);           // returns 6
 x.lastIndexOf(y, 6);        // returns 6
 x.lastIndexOf(y, 5);        // returns 2
 x.lastIndexOf(y, 1);        // returns -1

See also indexOf(), contains(), and count().

int QString.lastIndexOf (self, QStringRef str, int from = -1, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads lastIndexOf().

Returns the index position of the last occurrence of the string str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

 QString x = "crazy azimuths";
 QString y = "az";
 x.lastIndexOf(y);           // returns 6
 x.lastIndexOf(y, 6);        // returns 6
 x.lastIndexOf(y, 5);        // returns 2
 x.lastIndexOf(y, 1);        // returns -1

This function was introduced in Qt 4.5.

See also indexOf(), contains(), and count().

int QString.lastIndexOf (self, QLatin1String str, int from = -1, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads lastIndexOf().

Returns the index position of the last occurrence of the character ch, searching backward from position from.

int QString.lastIndexOf (self, QRegExp rx, int from = -1)

This function overloads lastIndexOf().

Returns the index position of the last occurrence of the string reference str in this string, searching backward from index position from. If from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 4.8.

See also indexOf(), contains(), and count().

QString QString.left (self, int len)

Returns a substring that contains the n leftmost characters of the string.

The entire string is returned if n is greater than size() or less than zero.

 QString x = "Pineapple";
 QString y = x.left(4);      // y == "Pine"

See also right(), mid(), and startsWith().

QString QString.leftJustified (self, int width, QChar fillChar = QLatin1Char(' '), bool truncate = False)

Returns a string of size width that contains this string padded by the fill character.

If truncate is false and the size() of the string is more than width, then the returned string is a copy of the string.

 QString s = "apple";
 QString t = s.leftJustified(8, '.');    // t == "apple..."

If truncate is true and the size() of the string is more than width, then any characters in a copy of the string after position width are removed, and the copy is returned.

 QString str = "Pineapple";
 str = str.leftJustified(5, '.', true);    // str == "Pinea"

See also rightJustified().

int QString.length (self)

Returns the number of characters in this string. Equivalent to size().

See also setLength() and resize().

int QString.localeAwareCompare (self, QString s)

Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

On Mac OS X since Qt 4.3, this function compares according the "Order for sorted lists" setting in the International prefereces panel.

See also compare() and QTextCodec.locale().

int QString.localeAwareCompare (self, QStringRef s)

This function overloads localeAwareCompare().

Compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

Same as localeAwareCompare(*this, other).

This function was introduced in Qt 4.5.

int QString.localeAwareCompare (QString s1, QString s2)

This function overloads localeAwareCompare().

Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

This function was introduced in Qt 4.5.

int QString.localeAwareCompare (QString s1, QStringRef s2)

This function overloads localeAwareCompare().

Compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

Same as localeAwareCompare(*this, other).

QString QString.mid (self, int position, int n = -1)

Returns a string that contains n characters of this string, starting at the specified position index.

Returns a null string if the position index exceeds the length of the string. If there are less than n characters available in the string starting at the given position, or if n is -1 (default), the function returns all characters that are available from the specified position.

Example:

 QString x = "Nine pineapples";
 QString y = x.mid(5, 4);            // y == "pine"
 QString z = x.mid(5);               // z == "pineapples"

See also left() and right().

QString QString.normalized (self, NormalizationForm mode)

Returns the string in the given Unicode normalization mode.

QString QString.normalized (self, NormalizationForm mode, QChar.UnicodeVersion version)

This is an overloaded function.

Returns the string in the given Unicode normalization mode, according to the given version of the Unicode standard.

QString QString.number (int n, int base = 10)

Returns a string equivalent of the number n according to the specified base.

The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.

 long a = 63;
 QString s = QString.number(a, 16);             // s == "3f"
 QString t = QString.number(a, 16).toUpper();     // t == "3F"

See also setNum().

QString QString.number (float n, str format = 'g', int precision = 6)

Returns a string equivalent of the number n, formatted according to the specified format and precision. See Argument Formats for details.

Unlike QLocale.toString(), this function does not honor the user's locale settings.

See also setNum() and QLocale.toString().

QString QString.number (int n, int base = 10)

This is an overloaded function.

QString QString.number (int n, int base = 10)

This is an overloaded function.

QString QString.prepend (self, QString s)

Prepends the string str to the beginning of this string and returns a reference to this string.

Example:

 QString x = "ship";
 QString y = "air";
 x.prepend(y);
 // x == "airship"

See also append() and insert().

QString QString.prepend (self, QLatin1String s)

This function overloads prepend().

Prepends the Latin-1 string str to this string.

QString QString.prepend (self, QByteArray s)

This function overloads prepend().

Prepends the byte array ba to this string. The byte array is converted to Unicode using the fromAscii() function.

You can disable this function by defining QT_NO_CAST_FROM_ASCII when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject.tr(), for example.

QString.push_back (self, QString s)

This function is provided for STL compatibility, appending the given other string onto the end of this string. It is equivalent to append(other).

See also append().

QString.push_front (self, QString s)

This function is provided for STL compatibility, prepending the given other string to the beginning of this string. It is equivalent to prepend(other).

See also prepend().

QString QString.remove (self, int i, int len)

Removes n characters from the string, starting at the given position index, and returns a reference to the string.

If the specified position index is within the string, but position + n is beyond the end of the string, the string is truncated at the specified position.

 QString s = "Montreal";
 s.remove(1, 4);
 // s == "Meal"

See also insert() and replace().

QString QString.remove (self, QString str, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Removes every occurrence of the character ch in this string, and returns a reference to this string.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Example:

 QString t = "Ali Baba";
 t.remove(QChar('a'), Qt.CaseInsensitive);
 // t == "li Bb"

This is the same as replace(ch, "", cs).

See also replace().

QString QString.remove (self, QRegExp rx)

Removes every occurrence of the given str string in this string, and returns a reference to this string.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This is the same as replace(str, "", cs).

See also replace().

QString QString.repeated (self, int times)

Returns a copy of this string repeated the specified number of times.

If times is less than 1, an empty string is returned.

Example:

 QString str("ab");
 str.repeated(4);            // returns "abababab"

This function was introduced in Qt 4.5.

QString QString.replace (self, int i, int len, QString after)

Replaces n characters beginning at index position with the string after and returns a reference to this string.

Example:

 QString x = "Say yes!";
 QString y = "no";
 x.replace(4, 3, y);
 // x == "Say no!"

See also insert() and remove().

QString QString.replace (self, QString before, QString after, Qt.CaseSensitivity cs = Qt.CaseSensitive)

QString QString.replace (self, QRegExp rx, QString after)

QString QString.replace (self, QLatin1String before, QLatin1String after, Qt.CaseSensitivity cs = Qt.CaseSensitive)

QString QString.replace (self, QLatin1String before, QString after, Qt.CaseSensitivity cs = Qt.CaseSensitive)

QString QString.replace (self, QString before, QLatin1String after, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads replace().

Replaces n characters beginning at index position with the first size characters of the QChar array unicode and returns a reference to this string.

QString.reserve (self, int asize)

Attempts to allocate memory for at least size characters. If you know in advance how large the string will be, you can call this function, and if you resize the string often you are likely to get better performance. If size is an underestimate, the worst that will happen is that the QString will be a bit slower.

The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the string, call resize().

This function is useful for code that needs to build up a long string and wants to avoid repeated reallocation. In this example, we want to add to the string until some condition is true, and we're fairly sure that size is large enough to make a call to reserve() worthwhile:

 QString result;
 int maxSize;
 bool condition;
 QChar nextChar;

 result.reserve(maxSize);

 while (condition)
     result.append(nextChar);

 result.squeeze();

See also squeeze() and capacity().

QString.resize (self, int size)

Sets the size of the string to size characters.

If size is greater than the current size, the string is extended to make it size characters long with the extra characters added to the end. The new characters are uninitialized.

If size is less than the current size, characters are removed from the end.

Example:

 QString s = "Hello world";
 s.resize(5);
 // s == "Hello"

 s.resize(8);
 // s == "Hello???" (where ? stands for any character)

If you want to append a certain number of identical characters to the string, use operator+=() as follows rather than resize():

 QString t = "Hello";
 t += QString(10, 'X');
 // t == "HelloXXXXXXXXXX"

If you want to expand the string so that it reaches a certain width and fill the new positions with a particular character, use the leftJustified() function:

If size is negative, it is equivalent to passing zero.

 QString r = "Hello";
 r = r.leftJustified(10, ' ');
 // r == "Hello     "

See also truncate() and reserve().

QString QString.right (self, int len)

Returns a substring that contains the n rightmost characters of the string.

The entire string is returned if n is greater than size() or less than zero.

 QString x = "Pineapple";
 QString y = x.right(5);      // y == "apple"

See also left(), mid(), and endsWith().

QString QString.rightJustified (self, int width, QChar fillChar = QLatin1Char(' '), bool truncate = False)

Returns a string of size() width that contains the fill character followed by the string. For example:

 QString s = "apple";
 QString t = s.rightJustified(8, '.');    // t == "...apple"

If truncate is false and the size() of the string is more than width, then the returned string is a copy of the string.

If truncate is true and the size() of the string is more than width, then the resulting string is truncated at position width.

 QString str = "Pineapple";
 str = str.rightJustified(5, '.', true);    // str == "Pinea"

See also leftJustified().

QString QString.section (self, QString sep, int start, int end = -1, SectionFlags flags = QString.SectionDefault)

This function returns a section of the string.

This string is treated as a sequence of fields separated by the character, sep. The returned string consists of the fields from position start to position end inclusive. If end is not specified, all fields from position start to the end of the string are included. Fields are numbered 0, 1, 2, etc., counting from the left, and -1, -2, etc., counting from right to left.

The flags argument can be used to affect some aspects of the function's behavior, e.g. whether to be case sensitive, whether to skip empty fields and how to deal with leading and trailing separators; see SectionFlags.

 QString str;
 QString csv = "forename,middlename,surname,phone";
 QString path = "/usr/local/bin/myapp"; // First field is empty
 QString.SectionFlag flag = QString.SectionSkipEmpty;

 str = csv.section(',', 2, 2);   // str == "surname"
 str = path.section('/', 3, 4);  // str == "bin/myapp"
 str = path.section('/', 3, 3, flag); // str == "myapp"

If start or end is negative, we count fields from the right of the string, the right-most field being -1, the one from right-most field being -2, and so on.

 str = csv.section(',', -3, -2);  // str == "middlename,surname"
 str = path.section('/', -1); // str == "myapp"

See also split().

QString QString.section (self, QRegExp reg, int start, int end = -1, SectionFlags flags = QString.SectionDefault)

This function overloads section().

 QString str;
 QString data = "forename**middlename**surname**phone";

 str = data.section("**", 2, 2); // str == "surname"
 str = data.section("**", -3, -2); // str == "middlename**surname"

See also split().

QString QString.setNum (self, int n, int base = 10)

Sets the string to the printed value of n in the specified base, and returns a reference to the string.

The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.

 QString str;
 str.setNum(1234);       // str == "1234"

The formatting always uses QLocale.C, i.e., English/UnitedStates. To get a localized string representation of a number, use QLocale.toString() with the appropriate locale.

QString QString.setNum (self, float n, str format = 'g', int precision = 6)

This is an overloaded function.

QString QString.setNum (self, int n, int base = 10)

This is an overloaded function.

QString QString.setNum (self, int n, int base = 10)

This is an overloaded function.

QString QString.simplified (self)

Returns a string that has whitespace removed from the start and the end, and that has each sequence of internal whitespace replaced with a single space.

Whitespace means any character for which QChar.isSpace() returns true. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.

Example:

 QString str = "  lots\t of\nwhitespace\r\n ";
 str = str.simplified();
 // str == "lots of whitespace";

See also trimmed().

int QString.size (self)

Returns the number of characters in this string.

The last character in the string is at position size() - 1. In addition, QString ensures that the character at position size() is always '\0', so that you can use the return value of data() and constData() as arguments to functions that expect '\0'-terminated strings.

Example:

 QString str = "World";
 int n = str.size();         // n == 5
 str.data()[0];              // returns 'W'
 str.data()[4];              // returns 'd'
 str.data()[5];              // returns '\0'

See also isEmpty() and resize().

QStringList QString.split (self, QString sep, SplitBehavior behavior = QString.KeepEmptyParts, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Splits the string into substrings wherever sep occurs, and returns the list of those strings. If sep does not match anywhere in the string, split() returns a single-element list containing this string.

cs specifies whether sep should be matched case sensitively or case insensitively.

If behavior is QString.SkipEmptyParts, empty entries don't appear in the result. By default, empty entries are kept.

Example:

 QString str = "a,,b,c";

 QStringList list1 = str.split(",");
 // list1: [ "a", "", "b", "c" ]

 QStringList list2 = str.split(",", QString.SkipEmptyParts);
 // list2: [ "a", "b", "c" ]

See also QStringList.join() and section().

QStringList QString.split (self, QRegExp sep, SplitBehavior behavior = QString.KeepEmptyParts)

This is an overloaded function.

QString.squeeze (self)

Releases any memory not required to store the character data.

The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function.

See also reserve() and capacity().

bool QString.startsWith (self, QString s, Qt.CaseSensitivity cs = Qt.CaseSensitive)

Returns true if the string starts with s; otherwise returns false.

If cs is Qt.CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

 QString str = "Bananas";
 str.startsWith("Ban");     // returns true
 str.startsWith("Car");     // returns false

See also endsWith().

bool QString.startsWith (self, QStringRef s, Qt.CaseSensitivity cs = Qt.CaseSensitive)

bool QString.startsWith (self, QLatin1String s, Qt.CaseSensitivity cs = Qt.CaseSensitive)

This function overloads startsWith().

QString.swap (self, QString other)

Swaps string other with this string. This operation is very fast and never fails.

This function was introduced in Qt 4.8.

QByteArray QString.toAscii (self)

Returns an 8-bit representation of the string as a QByteArray.

If a codec has been set using QTextCodec.setCodecForCStrings(), it is used to convert Unicode to 8-bit char; otherwise this function does the same as toLatin1().

Note that, despite the name, this function does not necessarily return an US-ASCII (ANSI X3.4-1986) string and its result may not be US-ASCII compatible.

See also fromAscii(), toLatin1(), toUtf8(), toLocal8Bit(), and QTextCodec.

QString QString.toCaseFolded (self)

Returns the case folded equivalent of the string. For most Unicode characters this is the same as toLower().

(float, bool ok) QString.toDouble (self)

Returns the string converted to a double value.

Returns 0.0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

 QString str = "1234.56";
 double val = str.toDouble();   // val == 1234.56

Various string formats for floating point numbers can be converted to double values:

 bool ok;
 double d;

 d = QString( "1234.56e-02" ).toDouble(&ok); // ok == true, d == 12.3456

This function tries to interpret the string according to the current locale. The current locale is determined from the system at application startup and can be changed by calling QLocale.setDefault(). If the string cannot be interpreted according to the current locale, this function falls back on the "C" locale.

 QLocale.setDefault(QLocale.C);
 d = QString( "1234,56" ).toDouble(&ok); // ok == false
 d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56

 QLocale.setDefault(QLocale.German);
 d = QString( "1234,56" ).toDouble(&ok); // ok == true, d == 1234.56
 d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56

Due to the ambiguity between the decimal point and thousands group separator in various locales, this function does not handle thousands group separators. If you need to convert such numbers, see QLocale.toDouble().

 QLocale.setDefault(QLocale.C);
 d = QString( "1234,56" ).toDouble(&ok); // ok == false

See also number(), QLocale.setDefault(), QLocale.toDouble(), and trimmed().

(float, bool ok) QString.toFloat (self)

Returns the string converted to a float value.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true. Returns 0.0 if the conversion fails.

Example:

 QString str1 = "1234.56";
 str1.toFloat();             // returns 1234.56

 bool ok;
 QString str2 = "R2D2";
 str2.toFloat(&ok);          // returns 0.0, sets ok to false

See also number(), toDouble(), and toInt().

(int, bool ok) QString.toInt (self, int base = 10)

Returns the string converted to an int using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;
 int hex = str.toInt(&ok, 16);       // hex == 255, ok == true
 int dec = str.toInt(&ok, 10);       // dec == 0, ok == false

See also number(), toUInt(), and toDouble().

QByteArray QString.toLatin1 (self)

Returns a Latin-1 representation of the string as a QByteArray.

The returned byte array is undefined if the string contains non-Latin1 characters. Those characters may be suppressed or replaced with a question mark.

See also fromLatin1(), toAscii(), toUtf8(), toLocal8Bit(), and QTextCodec.

QByteArray QString.toLocal8Bit (self)

Returns the local 8-bit representation of the string as a QByteArray. The returned byte array is undefined if the string contains characters not supported by the local 8-bit encoding.

QTextCodec.codecForLocale() is used to perform the conversion from Unicode. If the locale encoding could not be determined, this function does the same as toLatin1().

If this string contains any characters that cannot be encoded in the locale, the returned byte array is undefined. Those characters may be suppressed or replaced by another.

See also fromLocal8Bit(), toAscii(), toLatin1(), toUtf8(), and QTextCodec.

(int, bool ok) QString.toLong (self, int base = 10)

Returns the string converted to a long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;

 long hex = str.toLong(&ok, 16);     // hex == 255, ok == true
 long dec = str.toLong(&ok, 10);     // dec == 0, ok == false

See also number(), toULong(), and toInt().

(int, bool ok) QString.toLongLong (self, int base = 10)

Returns the string converted to a long long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;

 long hex = str.toLongLong(&ok, 16);      // hex == 255, ok == true
 long dec = str.toLongLong(&ok, 10);      // dec == 0, ok == false

See also number(), toULongLong(), and toInt().

QString QString.toLower (self)

Returns a lowercase copy of the string.

 QString str = "Qt by NOKIA";
 str = str.toLower();        // str == "qt by nokia"

The case conversion will always happen in the 'C' locale. For locale dependent case folding use QLocale.toLower()

See also toUpper() and QLocale.toLower().

(int, bool ok) QString.toShort (self, int base = 10)

Returns the string converted to a short using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;

 short hex = str.toShort(&ok, 16);   // hex == 255, ok == true
 short dec = str.toShort(&ok, 10);   // dec == 0, ok == false

See also number(), toUShort(), and toInt().

(int, bool ok) QString.toUInt (self, int base = 10)

Returns the string converted to an unsigned int using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;

 uint hex = str.toUInt(&ok, 16);     // hex == 255, ok == true
 uint dec = str.toUInt(&ok, 10);     // dec == 0, ok == false

See also number() and toInt().

(int, bool ok) QString.toULong (self, int base = 10)

Returns the string converted to an unsigned long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;

 ulong hex = str.toULong(&ok, 16);   // hex == 255, ok == true
 ulong dec = str.toULong(&ok, 10);   // dec == 0, ok == false

See also number().

(int, bool ok) QString.toULongLong (self, int base = 10)

Returns the string converted to an unsigned long long using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;

 unsigned long hex = str.toULongLong(&ok, 16);    // hex == 255, ok == true
 unsigned long dec = str.toULongLong(&ok, 10);    // dec == 0, ok == false

See also number() and toLongLong().

QString QString.toUpper (self)

Returns an uppercase copy of the string.

 QString str = "TeXt";
 str = str.toUpper();        // str == "TEXT"

The case conversion will always happen in the 'C' locale. For locale dependent case folding use QLocale.toUpper()

See also toLower() and QLocale.toLower().

(int, bool ok) QString.toUShort (self, int base = 10)

Returns the string converted to an unsigned short using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.

If base is 0, the C language convention is used: If the string begins with "0x", base 16 is used; if the string begins with "0", base 8 is used; otherwise, base 10 is used.

Example:

 QString str = "FF";
 bool ok;

 ushort hex = str.toUShort(&ok, 16);     // hex == 255, ok == true
 ushort dec = str.toUShort(&ok, 10);     // dec == 0, ok == false

See also number() and toShort().

QByteArray QString.toUtf8 (self)

Returns a UTF-8 representation of the string as a QByteArray.

UTF-8 is a Unicode codec and can represent all characters in a Unicode string like QString.

However, in the Unicode range, there are certain codepoints that are not considered characters. The Unicode standard reserves the last two codepoints in each Unicode Plane (U+FFFE, U+FFFF, U+1FFFE, U+1FFFF, U+2FFFE, etc.), as well as 16 codepoints in the range U+FDD0..U+FDDF, inclusive, as non-characters. If any of those appear in the string, they may be discarded and will not appear in the UTF-8 representation, or they may be replaced by one or more replacement characters.

See also fromUtf8(), toAscii(), toLatin1(), toLocal8Bit(), and QTextCodec.

QString QString.trimmed (self)

Returns a string that has whitespace removed from the start and the end.

Whitespace means any character for which QChar.isSpace() returns true. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.

Example:

 QString str = "  lots\t of\nwhitespace\r\n ";
 str = str.trimmed();
 // str == "lots\t of\nwhitespace"

Unlike simplified(), trimmed() leaves internal whitespace alone.

See also simplified().

QString.truncate (self, int pos)

Truncates the string at the given position index.

If the specified position index is beyond the end of the string, nothing happens.

Example:

 QString str = "Vladivostok";
 str.truncate(4);
 // str == "Vlad"

If position is negative, it is equivalent to passing zero.

See also chop(), resize(), and left().

QString QString.__add__ (self, QString s2)

QString QString.__add__ (self, QByteArray ba)

int QString.__contains__ (self, QString s)

bool QString.__eq__ (self, QString s)

bool QString.__eq__ (self, QLatin1String s)

bool QString.__eq__ (self, QByteArray s)

bool QString.__eq__ (self, QStringRef s2)

bool QString.__ge__ (self, QString s)

bool QString.__ge__ (self, QLatin1String s)

bool QString.__ge__ (self, QByteArray s)

QString QString.__getitem__ (self, int i)

QString QString.__getitem__ (self, slice slice)

bool QString.__gt__ (self, QString s)

bool QString.__gt__ (self, QLatin1String s)

bool QString.__gt__ (self, QByteArray s)

int QString.__hash__ (self)

QString QString.__iadd__ (self, QChar.SpecialCharacter c)

QString QString.__iadd__ (self, QString s)

QString QString.__iadd__ (self, QLatin1String s)

QString QString.__iadd__ (self, QByteArray s)

QString QString.__imul__ (self, int m)

bool QString.__le__ (self, QString s)

bool QString.__le__ (self, QLatin1String s)

bool QString.__le__ (self, QByteArray s)

QString.__len__ (self)

bool QString.__lt__ (self, QString s)

bool QString.__lt__ (self, QLatin1String s)

bool QString.__lt__ (self, QByteArray s)

QString QString.__mul__ (self, int m)

bool QString.__ne__ (self, QString s)

bool QString.__ne__ (self, QLatin1String s)

bool QString.__ne__ (self, QByteArray s)

bool QString.__ne__ (self, QStringRef s2)

str QString.__repr__ (self)

str QString.__str__ (self)

unicode QString.__unicode__ (self)

PyQt 4.10.1 for MacOSCopyright © Riverbank Computing Ltd and Nokia 2012Qt 4.8.4