diff -r ffa851df0825 -r 2fb8b9db1c86 symbian-qemu-0.9.1-12/python-2.6.1/Doc/library/string.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/symbian-qemu-0.9.1-12/python-2.6.1/Doc/library/string.rst Fri Jul 31 15:01:17 2009 +0100 @@ -0,0 +1,849 @@ +:mod:`string` --- Common string operations +========================================== + +.. module:: string + :synopsis: Common string operations. + + +.. index:: module: re + +The :mod:`string` module contains a number of useful constants and +classes, as well as some deprecated legacy functions that are also +available as methods on strings. In addition, Python's built-in string +classes support the sequence type methods described in the +:ref:`typesseq` section, and also the string-specific methods described +in the :ref:`string-methods` section. To output formatted strings use +template strings or the ``%`` operator described in the +:ref:`string-formatting` section. Also, see the :mod:`re` module for +string functions based on regular expressions. + + +String constants +---------------- + +The constants defined in this module are: + + +.. data:: ascii_letters + + The concatenation of the :const:`ascii_lowercase` and :const:`ascii_uppercase` + constants described below. This value is not locale-dependent. + + +.. data:: ascii_lowercase + + The lowercase letters ``'abcdefghijklmnopqrstuvwxyz'``. This value is not + locale-dependent and will not change. + + +.. data:: ascii_uppercase + + The uppercase letters ``'ABCDEFGHIJKLMNOPQRSTUVWXYZ'``. This value is not + locale-dependent and will not change. + + +.. data:: digits + + The string ``'0123456789'``. + + +.. data:: hexdigits + + The string ``'0123456789abcdefABCDEF'``. + + +.. data:: letters + + The concatenation of the strings :const:`lowercase` and :const:`uppercase` + described below. The specific value is locale-dependent, and will be updated + when :func:`locale.setlocale` is called. + + +.. data:: lowercase + + A string containing all the characters that are considered lowercase letters. + On most systems this is the string ``'abcdefghijklmnopqrstuvwxyz'``. Do not + change its definition --- the effect on the routines :func:`upper` and + :func:`swapcase` is undefined. The specific value is locale-dependent, and will + be updated when :func:`locale.setlocale` is called. + + +.. data:: octdigits + + The string ``'01234567'``. + + +.. data:: punctuation + + String of ASCII characters which are considered punctuation characters in the + ``C`` locale. + + +.. data:: printable + + String of characters which are considered printable. This is a combination of + :const:`digits`, :const:`letters`, :const:`punctuation`, and + :const:`whitespace`. + + +.. data:: uppercase + + A string containing all the characters that are considered uppercase letters. + On most systems this is the string ``'ABCDEFGHIJKLMNOPQRSTUVWXYZ'``. Do not + change its definition --- the effect on the routines :func:`lower` and + :func:`swapcase` is undefined. The specific value is locale-dependent, and will + be updated when :func:`locale.setlocale` is called. + + +.. data:: whitespace + + A string containing all characters that are considered whitespace. On most + systems this includes the characters space, tab, linefeed, return, formfeed, and + vertical tab. Do not change its definition --- the effect on the routines + :func:`strip` and :func:`split` is undefined. + + +.. _new-string-formatting: + +String Formatting +----------------- + +Starting in Python 2.6, the built-in str and unicode classes provide the ability +to do complex variable substitutions and value formatting via the +:meth:`str.format` method described in :pep:`3101`. The :class:`Formatter` +class in the :mod:`string` module allows you to create and customize your own +string formatting behaviors using the same implementation as the built-in +:meth:`format` method. + +.. class:: Formatter + + The :class:`Formatter` class has the following public methods: + + .. method:: format(format_string, *args, *kwargs) + + :meth:`format` is the primary API method. It takes a format template + string, and an arbitrary set of positional and keyword argument. + :meth:`format` is just a wrapper that calls :meth:`vformat`. + + .. method:: vformat(format_string, args, kwargs) + + This function does the actual work of formatting. It is exposed as a + separate function for cases where you want to pass in a predefined + dictionary of arguments, rather than unpacking and repacking the + dictionary as individual arguments using the ``*args`` and ``**kwds`` + syntax. :meth:`vformat` does the work of breaking up the format template + string into character data and replacement fields. It calls the various + methods described below. + + In addition, the :class:`Formatter` defines a number of methods that are + intended to be replaced by subclasses: + + .. method:: parse(format_string) + + Loop over the format_string and return an iterable of tuples + (*literal_text*, *field_name*, *format_spec*, *conversion*). This is used + by :meth:`vformat` to break the string in to either literal text, or + replacement fields. + + The values in the tuple conceptually represent a span of literal text + followed by a single replacement field. If there is no literal text + (which can happen if two replacement fields occur consecutively), then + *literal_text* will be a zero-length string. If there is no replacement + field, then the values of *field_name*, *format_spec* and *conversion* + will be ``None``. + + .. method:: get_field(field_name, args, kwargs) + + Given *field_name* as returned by :meth:`parse` (see above), convert it to + an object to be formatted. Returns a tuple (obj, used_key). The default + version takes strings of the form defined in :pep:`3101`, such as + "0[name]" or "label.title". *args* and *kwargs* are as passed in to + :meth:`vformat`. The return value *used_key* has the same meaning as the + *key* parameter to :meth:`get_value`. + + .. method:: get_value(key, args, kwargs) + + Retrieve a given field value. The *key* argument will be either an + integer or a string. If it is an integer, it represents the index of the + positional argument in *args*; if it is a string, then it represents a + named argument in *kwargs*. + + The *args* parameter is set to the list of positional arguments to + :meth:`vformat`, and the *kwargs* parameter is set to the dictionary of + keyword arguments. + + For compound field names, these functions are only called for the first + component of the field name; Subsequent components are handled through + normal attribute and indexing operations. + + So for example, the field expression '0.name' would cause + :meth:`get_value` to be called with a *key* argument of 0. The ``name`` + attribute will be looked up after :meth:`get_value` returns by calling the + built-in :func:`getattr` function. + + If the index or keyword refers to an item that does not exist, then an + :exc:`IndexError` or :exc:`KeyError` should be raised. + + .. method:: check_unused_args(used_args, args, kwargs) + + Implement checking for unused arguments if desired. The arguments to this + function is the set of all argument keys that were actually referred to in + the format string (integers for positional arguments, and strings for + named arguments), and a reference to the *args* and *kwargs* that was + passed to vformat. The set of unused args can be calculated from these + parameters. :meth:`check_unused_args` is assumed to throw an exception if + the check fails. + + .. method:: format_field(value, format_spec) + + :meth:`format_field` simply calls the global :func:`format` built-in. The + method is provided so that subclasses can override it. + + .. method:: convert_field(value, conversion) + + Converts the value (returned by :meth:`get_field`) given a conversion type + (as in the tuple returned by the :meth:`parse` method.) The default + version understands 'r' (repr) and 's' (str) conversion types. + + +.. _formatstrings: + +Format String Syntax +-------------------- + +The :meth:`str.format` method and the :class:`Formatter` class share the same +syntax for format strings (although in the case of :class:`Formatter`, +subclasses can define their own format string syntax.) + +Format strings contain "replacement fields" surrounded by curly braces ``{}``. +Anything that is not contained in braces is considered literal text, which is +copied unchanged to the output. If you need to include a brace character in the +literal text, it can be escaped by doubling: ``{{`` and ``}}``. + +The grammar for a replacement field is as follows: + + .. productionlist:: sf + replacement_field: "{" `field_name` ["!" `conversion`] [":" `format_spec`] "}" + field_name: (`identifier` | `integer`) ("." `attribute_name` | "[" element_index "]")* + attribute_name: `identifier` + element_index: `integer` + conversion: "r" | "s" + format_spec: + +In less formal terms, the replacement field starts with a *field_name*, which +can either be a number (for a positional argument), or an identifier (for +keyword arguments). Following this is an optional *conversion* field, which is +preceded by an exclamation point ``'!'``, and a *format_spec*, which is preceded +by a colon ``':'``. + +The *field_name* itself begins with either a number or a keyword. If it's a +number, it refers to a positional argument, and if it's a keyword it refers to a +named keyword argument. This can be followed by any number of index or +attribute expressions. An expression of the form ``'.name'`` selects the named +attribute using :func:`getattr`, while an expression of the form ``'[index]'`` +does an index lookup using :func:`__getitem__`. + +Some simple format string examples:: + + "First, thou shalt count to {0}" # References first positional argument + "My quest is {name}" # References keyword argument 'name' + "Weight in tons {0.weight}" # 'weight' attribute of first positional arg + "Units destroyed: {players[0]}" # First element of keyword argument 'players'. + +The *conversion* field causes a type coercion before formatting. Normally, the +job of formatting a value is done by the :meth:`__format__` method of the value +itself. However, in some cases it is desirable to force a type to be formatted +as a string, overriding its own definition of formatting. By converting the +value to a string before calling :meth:`__format__`, the normal formatting logic +is bypassed. + +Two conversion flags are currently supported: ``'!s'`` which calls :func:`str` +on the value, and ``'!r'`` which calls :func:`repr`. + +Some examples:: + + "Harold's a clever {0!s}" # Calls str() on the argument first + "Bring out the holy {name!r}" # Calls repr() on the argument first + +The *format_spec* field contains a specification of how the value should be +presented, including such details as field width, alignment, padding, decimal +precision and so on. Each value type can define it's own "formatting +mini-language" or interpretation of the *format_spec*. + +Most built-in types support a common formatting mini-language, which is +described in the next section. + +A *format_spec* field can also include nested replacement fields within it. +These nested replacement fields can contain only a field name; conversion flags +and format specifications are not allowed. The replacement fields within the +format_spec are substituted before the *format_spec* string is interpreted. +This allows the formatting of a value to be dynamically specified. + +For example, suppose you wanted to have a replacement field whose field width is +determined by another variable:: + + "A man with two {0:{1}}".format("noses", 10) + +This would first evaluate the inner replacement field, making the format string +effectively:: + + "A man with two {0:10}" + +Then the outer replacement field would be evaluated, producing:: + + "noses " + +Which is substituted into the string, yielding:: + + "A man with two noses " + +(The extra space is because we specified a field width of 10, and because left +alignment is the default for strings.) + + +.. _formatspec: + +Format Specification Mini-Language +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +"Format specifications" are used within replacement fields contained within a +format string to define how individual values are presented (see +:ref:`formatstrings`.) They can also be passed directly to the builtin +:func:`format` function. Each formattable type may define how the format +specification is to be interpreted. + +Most built-in types implement the following options for format specifications, +although some of the formatting options are only supported by the numeric types. + +A general convention is that an empty format string (``""``) produces the same +result as if you had called :func:`str` on the value. + +The general form of a *standard format specifier* is: + +.. productionlist:: sf + format_spec: [[`fill`]`align`][`sign`][#][0][`width`][.`precision`][`type`] + fill: + align: "<" | ">" | "=" | "^" + sign: "+" | "-" | " " + width: `integer` + precision: `integer` + type: "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "x" | "X" | "%" + +The *fill* character can be any character other than '}' (which signifies the +end of the field). The presence of a fill character is signaled by the *next* +character, which must be one of the alignment options. If the second character +of *format_spec* is not a valid alignment option, then it is assumed that both +the fill character and the alignment option are absent. + +The meaning of the various alignment options is as follows: + + +---------+----------------------------------------------------------+ + | Option | Meaning | + +=========+==========================================================+ + | ``'<'`` | Forces the field to be left-aligned within the available | + | | space (This is the default.) | + +---------+----------------------------------------------------------+ + | ``'>'`` | Forces the field to be right-aligned within the | + | | available space. | + +---------+----------------------------------------------------------+ + | ``'='`` | Forces the padding to be placed after the sign (if any) | + | | but before the digits. This is used for printing fields | + | | in the form '+000000120'. This alignment option is only | + | | valid for numeric types. | + +---------+----------------------------------------------------------+ + | ``'^'`` | Forces the field to be centered within the available | + | | space. | + +---------+----------------------------------------------------------+ + +Note that unless a minimum field width is defined, the field width will always +be the same size as the data to fill it, so that the alignment option has no +meaning in this case. + +The *sign* option is only valid for number types, and can be one of the +following: + + +---------+----------------------------------------------------------+ + | Option | Meaning | + +=========+==========================================================+ + | ``'+'`` | indicates that a sign should be used for both | + | | positive as well as negative numbers. | + +---------+----------------------------------------------------------+ + | ``'-'`` | indicates that a sign should be used only for negative | + | | numbers (this is the default behavior). | + +---------+----------------------------------------------------------+ + | space | indicates that a leading space should be used on | + | | positive numbers, and a minus sign on negative numbers. | + +---------+----------------------------------------------------------+ + +The ``'#'`` option is only valid for integers, and only for binary, octal, or +hexadecimal output. If present, it specifies that the output will be prefixed +by ``'0b'``, ``'0o'``, or ``'0x'``, respectively. + +*width* is a decimal integer defining the minimum field width. If not +specified, then the field width will be determined by the content. + +If the *width* field is preceded by a zero (``'0'``) character, this enables +zero-padding. This is equivalent to an *alignment* type of ``'='`` and a *fill* +character of ``'0'``. + +The *precision* is a decimal number indicating how many digits should be +displayed after the decimal point for a floating point value formatted with +``'f'`` and ``'F'``, or before and after the decimal point for a floating point +value formatted with ``'g'`` or ``'G'``. For non-number types the field +indicates the maximum field size - in other words, how many characters will be +used from the field content. The *precision* is ignored for integer values. + +Finally, the *type* determines how the data should be presented. + +The available integer presentation types are: + + +---------+----------------------------------------------------------+ + | Type | Meaning | + +=========+==========================================================+ + | ``'b'`` | Binary format. Outputs the number in base 2. | + +---------+----------------------------------------------------------+ + | ``'c'`` | Character. Converts the integer to the corresponding | + | | unicode character before printing. | + +---------+----------------------------------------------------------+ + | ``'d'`` | Decimal Integer. Outputs the number in base 10. | + +---------+----------------------------------------------------------+ + | ``'o'`` | Octal format. Outputs the number in base 8. | + +---------+----------------------------------------------------------+ + | ``'x'`` | Hex format. Outputs the number in base 16, using lower- | + | | case letters for the digits above 9. | + +---------+----------------------------------------------------------+ + | ``'X'`` | Hex format. Outputs the number in base 16, using upper- | + | | case letters for the digits above 9. | + +---------+----------------------------------------------------------+ + | ``'n'`` | Number. This is the same as ``'d'``, except that it uses | + | | the current locale setting to insert the appropriate | + | | number separator characters. | + +---------+----------------------------------------------------------+ + | None | The same as ``'d'``. | + +---------+----------------------------------------------------------+ + +The available presentation types for floating point and decimal values are: + + +---------+----------------------------------------------------------+ + | Type | Meaning | + +=========+==========================================================+ + | ``'e'`` | Exponent notation. Prints the number in scientific | + | | notation using the letter 'e' to indicate the exponent. | + +---------+----------------------------------------------------------+ + | ``'E'`` | Exponent notation. Same as ``'e'`` except it uses an | + | | upper case 'E' as the separator character. | + +---------+----------------------------------------------------------+ + | ``'f'`` | Fixed point. Displays the number as a fixed-point | + | | number. | + +---------+----------------------------------------------------------+ + | ``'F'`` | Fixed point. Same as ``'f'``. | + +---------+----------------------------------------------------------+ + | ``'g'`` | General format. This prints the number as a fixed-point | + | | number, unless the number is too large, in which case | + | | it switches to ``'e'`` exponent notation. Infinity and | + | | NaN values are formatted as ``inf``, ``-inf`` and | + | | ``nan``, respectively. | + +---------+----------------------------------------------------------+ + | ``'G'`` | General format. Same as ``'g'`` except switches to | + | | ``'E'`` if the number gets to large. The representations | + | | of infinity and NaN are uppercased, too. | + +---------+----------------------------------------------------------+ + | ``'n'`` | Number. This is the same as ``'g'``, except that it uses | + | | the current locale setting to insert the appropriate | + | | number separator characters. | + +---------+----------------------------------------------------------+ + | ``'%'`` | Percentage. Multiplies the number by 100 and displays | + | | in fixed (``'f'``) format, followed by a percent sign. | + +---------+----------------------------------------------------------+ + | None | The same as ``'g'``. | + +---------+----------------------------------------------------------+ + + +Template strings +---------------- + +Templates provide simpler string substitutions as described in :pep:`292`. +Instead of the normal ``%``\ -based substitutions, Templates support ``$``\ +-based substitutions, using the following rules: + +* ``$$`` is an escape; it is replaced with a single ``$``. + +* ``$identifier`` names a substitution placeholder matching a mapping key of + ``"identifier"``. By default, ``"identifier"`` must spell a Python + identifier. The first non-identifier character after the ``$`` character + terminates this placeholder specification. + +* ``${identifier}`` is equivalent to ``$identifier``. It is required when valid + identifier characters follow the placeholder but are not part of the + placeholder, such as ``"${noun}ification"``. + +Any other appearance of ``$`` in the string will result in a :exc:`ValueError` +being raised. + +.. versionadded:: 2.4 + +The :mod:`string` module provides a :class:`Template` class that implements +these rules. The methods of :class:`Template` are: + + +.. class:: Template(template) + + The constructor takes a single argument which is the template string. + + + .. method:: substitute(mapping[, **kws]) + + Performs the template substitution, returning a new string. *mapping* is + any dictionary-like object with keys that match the placeholders in the + template. Alternatively, you can provide keyword arguments, where the + keywords are the placeholders. When both *mapping* and *kws* are given + and there are duplicates, the placeholders from *kws* take precedence. + + + .. method:: safe_substitute(mapping[, **kws]) + + Like :meth:`substitute`, except that if placeholders are missing from + *mapping* and *kws*, instead of raising a :exc:`KeyError` exception, the + original placeholder will appear in the resulting string intact. Also, + unlike with :meth:`substitute`, any other appearances of the ``$`` will + simply return ``$`` instead of raising :exc:`ValueError`. + + While other exceptions may still occur, this method is called "safe" + because substitutions always tries to return a usable string instead of + raising an exception. In another sense, :meth:`safe_substitute` may be + anything other than safe, since it will silently ignore malformed + templates containing dangling delimiters, unmatched braces, or + placeholders that are not valid Python identifiers. + +:class:`Template` instances also provide one public data attribute: + + +.. attribute:: string.template + + This is the object passed to the constructor's *template* argument. In general, + you shouldn't change it, but read-only access is not enforced. + +Here is an example of how to use a Template: + + >>> from string import Template + >>> s = Template('$who likes $what') + >>> s.substitute(who='tim', what='kung pao') + 'tim likes kung pao' + >>> d = dict(who='tim') + >>> Template('Give $who $100').substitute(d) + Traceback (most recent call last): + [...] + ValueError: Invalid placeholder in string: line 1, col 10 + >>> Template('$who likes $what').substitute(d) + Traceback (most recent call last): + [...] + KeyError: 'what' + >>> Template('$who likes $what').safe_substitute(d) + 'tim likes $what' + +Advanced usage: you can derive subclasses of :class:`Template` to customize the +placeholder syntax, delimiter character, or the entire regular expression used +to parse template strings. To do this, you can override these class attributes: + +* *delimiter* -- This is the literal string describing a placeholder introducing + delimiter. The default value ``$``. Note that this should *not* be a regular + expression, as the implementation will call :meth:`re.escape` on this string as + needed. + +* *idpattern* -- This is the regular expression describing the pattern for + non-braced placeholders (the braces will be added automatically as + appropriate). The default value is the regular expression + ``[_a-z][_a-z0-9]*``. + +Alternatively, you can provide the entire regular expression pattern by +overriding the class attribute *pattern*. If you do this, the value must be a +regular expression object with four named capturing groups. The capturing +groups correspond to the rules given above, along with the invalid placeholder +rule: + +* *escaped* -- This group matches the escape sequence, e.g. ``$$``, in the + default pattern. + +* *named* -- This group matches the unbraced placeholder name; it should not + include the delimiter in capturing group. + +* *braced* -- This group matches the brace enclosed placeholder name; it should + not include either the delimiter or braces in the capturing group. + +* *invalid* -- This group matches any other delimiter pattern (usually a single + delimiter), and it should appear last in the regular expression. + + +String functions +---------------- + +The following functions are available to operate on string and Unicode objects. +They are not available as string methods. + + +.. function:: capwords(s) + + Split the argument into words using :func:`split`, capitalize each word using + :func:`capitalize`, and join the capitalized words using :func:`join`. Note + that this replaces runs of whitespace characters by a single space, and removes + leading and trailing whitespace. + + +.. function:: maketrans(from, to) + + Return a translation table suitable for passing to :func:`translate`, that will + map each character in *from* into the character at the same position in *to*; + *from* and *to* must have the same length. + + .. warning:: + + Don't use strings derived from :const:`lowercase` and :const:`uppercase` as + arguments; in some locales, these don't have the same length. For case + conversions, always use :func:`lower` and :func:`upper`. + + +Deprecated string functions +--------------------------- + +The following list of functions are also defined as methods of string and +Unicode objects; see section :ref:`string-methods` for more information on +those. You should consider these functions as deprecated, although they will +not be removed until Python 3.0. The functions defined in this module are: + + +.. function:: atof(s) + + .. deprecated:: 2.0 + Use the :func:`float` built-in function. + + .. index:: builtin: float + + Convert a string to a floating point number. The string must have the standard + syntax for a floating point literal in Python, optionally preceded by a sign + (``+`` or ``-``). Note that this behaves identical to the built-in function + :func:`float` when passed a string. + + .. note:: + + .. index:: + single: NaN + single: Infinity + + When passing in a string, values for NaN and Infinity may be returned, depending + on the underlying C library. The specific set of strings accepted which cause + these values to be returned depends entirely on the C library and is known to + vary. + + +.. function:: atoi(s[, base]) + + .. deprecated:: 2.0 + Use the :func:`int` built-in function. + + .. index:: builtin: eval + + Convert string *s* to an integer in the given *base*. The string must consist + of one or more digits, optionally preceded by a sign (``+`` or ``-``). The + *base* defaults to 10. If it is 0, a default base is chosen depending on the + leading characters of the string (after stripping the sign): ``0x`` or ``0X`` + means 16, ``0`` means 8, anything else means 10. If *base* is 16, a leading + ``0x`` or ``0X`` is always accepted, though not required. This behaves + identically to the built-in function :func:`int` when passed a string. (Also + note: for a more flexible interpretation of numeric literals, use the built-in + function :func:`eval`.) + + +.. function:: atol(s[, base]) + + .. deprecated:: 2.0 + Use the :func:`long` built-in function. + + .. index:: builtin: long + + Convert string *s* to a long integer in the given *base*. The string must + consist of one or more digits, optionally preceded by a sign (``+`` or ``-``). + The *base* argument has the same meaning as for :func:`atoi`. A trailing ``l`` + or ``L`` is not allowed, except if the base is 0. Note that when invoked + without *base* or with *base* set to 10, this behaves identical to the built-in + function :func:`long` when passed a string. + + +.. function:: capitalize(word) + + Return a copy of *word* with only its first character capitalized. + + +.. function:: expandtabs(s[, tabsize]) + + Expand tabs in a string replacing them by one or more spaces, depending on the + current column and the given tab size. The column number is reset to zero after + each newline occurring in the string. This doesn't understand other non-printing + characters or escape sequences. The tab size defaults to 8. + + +.. function:: find(s, sub[, start[,end]]) + + Return the lowest index in *s* where the substring *sub* is found such that + *sub* is wholly contained in ``s[start:end]``. Return ``-1`` on failure. + Defaults for *start* and *end* and interpretation of negative values is the same + as for slices. + + +.. function:: rfind(s, sub[, start[, end]]) + + Like :func:`find` but find the highest index. + + +.. function:: index(s, sub[, start[, end]]) + + Like :func:`find` but raise :exc:`ValueError` when the substring is not found. + + +.. function:: rindex(s, sub[, start[, end]]) + + Like :func:`rfind` but raise :exc:`ValueError` when the substring is not found. + + +.. function:: count(s, sub[, start[, end]]) + + Return the number of (non-overlapping) occurrences of substring *sub* in string + ``s[start:end]``. Defaults for *start* and *end* and interpretation of negative + values are the same as for slices. + + +.. function:: lower(s) + + Return a copy of *s*, but with upper case letters converted to lower case. + + +.. function:: split(s[, sep[, maxsplit]]) + + Return a list of the words of the string *s*. If the optional second argument + *sep* is absent or ``None``, the words are separated by arbitrary strings of + whitespace characters (space, tab, newline, return, formfeed). If the second + argument *sep* is present and not ``None``, it specifies a string to be used as + the word separator. The returned list will then have one more item than the + number of non-overlapping occurrences of the separator in the string. The + optional third argument *maxsplit* defaults to 0. If it is nonzero, at most + *maxsplit* number of splits occur, and the remainder of the string is returned + as the final element of the list (thus, the list will have at most + ``maxsplit+1`` elements). + + The behavior of split on an empty string depends on the value of *sep*. If *sep* + is not specified, or specified as ``None``, the result will be an empty list. + If *sep* is specified as any string, the result will be a list containing one + element which is an empty string. + + +.. function:: rsplit(s[, sep[, maxsplit]]) + + Return a list of the words of the string *s*, scanning *s* from the end. To all + intents and purposes, the resulting list of words is the same as returned by + :func:`split`, except when the optional third argument *maxsplit* is explicitly + specified and nonzero. When *maxsplit* is nonzero, at most *maxsplit* number of + splits -- the *rightmost* ones -- occur, and the remainder of the string is + returned as the first element of the list (thus, the list will have at most + ``maxsplit+1`` elements). + + .. versionadded:: 2.4 + + +.. function:: splitfields(s[, sep[, maxsplit]]) + + This function behaves identically to :func:`split`. (In the past, :func:`split` + was only used with one argument, while :func:`splitfields` was only used with + two arguments.) + + +.. function:: join(words[, sep]) + + Concatenate a list or tuple of words with intervening occurrences of *sep*. + The default value for *sep* is a single space character. It is always true that + ``string.join(string.split(s, sep), sep)`` equals *s*. + + +.. function:: joinfields(words[, sep]) + + This function behaves identically to :func:`join`. (In the past, :func:`join` + was only used with one argument, while :func:`joinfields` was only used with two + arguments.) Note that there is no :meth:`joinfields` method on string objects; + use the :meth:`join` method instead. + + +.. function:: lstrip(s[, chars]) + + Return a copy of the string with leading characters removed. If *chars* is + omitted or ``None``, whitespace characters are removed. If given and not + ``None``, *chars* must be a string; the characters in the string will be + stripped from the beginning of the string this method is called on. + + .. versionchanged:: 2.2.3 + The *chars* parameter was added. The *chars* parameter cannot be passed in + earlier 2.2 versions. + + +.. function:: rstrip(s[, chars]) + + Return a copy of the string with trailing characters removed. If *chars* is + omitted or ``None``, whitespace characters are removed. If given and not + ``None``, *chars* must be a string; the characters in the string will be + stripped from the end of the string this method is called on. + + .. versionchanged:: 2.2.3 + The *chars* parameter was added. The *chars* parameter cannot be passed in + earlier 2.2 versions. + + +.. function:: strip(s[, chars]) + + Return a copy of the string with leading and trailing characters removed. If + *chars* is omitted or ``None``, whitespace characters are removed. If given and + not ``None``, *chars* must be a string; the characters in the string will be + stripped from the both ends of the string this method is called on. + + .. versionchanged:: 2.2.3 + The *chars* parameter was added. The *chars* parameter cannot be passed in + earlier 2.2 versions. + + +.. function:: swapcase(s) + + Return a copy of *s*, but with lower case letters converted to upper case and + vice versa. + + +.. function:: translate(s, table[, deletechars]) + + Delete all characters from *s* that are in *deletechars* (if present), and then + translate the characters using *table*, which must be a 256-character string + giving the translation for each character value, indexed by its ordinal. If + *table* is ``None``, then only the character deletion step is performed. + + +.. function:: upper(s) + + Return a copy of *s*, but with lower case letters converted to upper case. + + +.. function:: ljust(s, width) + rjust(s, width) + center(s, width) + + These functions respectively left-justify, right-justify and center a string in + a field of given width. They return a string that is at least *width* + characters wide, created by padding the string *s* with spaces until the given + width on the right, left or both sides. The string is never truncated. + + +.. function:: zfill(s, width) + + Pad a numeric string on the left with zero digits until the given width is + reached. Strings starting with a sign are handled correctly. + + +.. function:: replace(str, old, new[, maxreplace]) + + Return a copy of string *str* with all occurrences of substring *old* replaced + by *new*. If the optional argument *maxreplace* is given, the first + *maxreplace* occurrences are replaced. +