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'``.  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'``.  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.

String Formatting

.. versionadded:: 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.

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 string and
   an arbitrary set of positional and keyword arguments.
   :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 ``**kwargs``
   syntax.  :meth:`vformat` does the work of breaking up the format 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 into 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 raise 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 's' (str), 'r' (repr) and 'a' (ascii) conversion
   types.

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: arg_name ("." `attribute_name` | "[" `element_index` "]")*
   arg_name: [`identifier` | `integer`]
   attribute_name: `identifier`
   element_index: `integer` | `index_string`
   index_string: <any source character except "]"> +
   conversion: "r" | "s"
   format_spec: <described in the next section>

In less formal terms, the replacement field can start with a field_name that specifies the object whose value is to be formatted and inserted into the output instead of the replacement field. The field_name is optionally followed by a conversion field, which is preceded by an exclamation point '!', and a format_spec, which is preceded by a colon ':'. These specify a non-default format for the replacement value.

See also the :ref:`formatspec` section.

The field_name itself begins with an arg_name that is 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. If the numerical arg_names in a format string are 0, 1, 2, ... in sequence, they can all be omitted (not just some) and the numbers 0, 1, 2, ... will be automatically inserted in that order. Because arg_name is not quote-delimited, it is not possible to specify arbitrary dictionary keys (e.g., the strings '10' or ':-]') within a format string. The arg_name 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__`.

.. versionchanged:: 2.7
   The positional argument specifiers can be omitted, so ``'{} {}'`` is
   equivalent to ``'{0} {1}'``.

Some simple format string examples:

"First, thou shalt count to {0}" # References first positional argument
"Bring me a {}"                  # Implicitly references the first positional argument
"From {} to {}"                  # Same as "From {0} to {1}"
"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 its 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.

See the :ref:`formatexamples` section for some examples.

.. productionlist:: sf
   format_spec: [[`fill`]`align`][`sign`][#][0][`width`][,][.`precision`][`type`]
   fill: <any character>
   align: "<" | ">" | "=" | "^"
   sign: "+" | "-" | " "
   width: `integer`
   precision: `integer`
   type: "b" | "c" | "d" | "e" | "E" | "f" | "F" | "g" | "G" | "n" | "o" | "s" | "x" | "X" | "%"

.. versionchanged:: 2.7
   Added the ``','`` option (see also :pep:`378`).

>>> '{0}, {1}, {2}'.format('a', 'b', 'c')
'a, b, c'
>>> '{}, {}, {}'.format('a', 'b', 'c')  # 2.7+ only
'a, b, c'
>>> '{2}, {1}, {0}'.format('a', 'b', 'c')
'c, b, a'
>>> '{2}, {1}, {0}'.format(*'abc')      # unpacking argument sequence
'c, b, a'
>>> '{0}{1}{0}'.format('abra', 'cad')   # arguments' indices can be repeated
'abracadabra'

>>> 'Coordinates: {latitude}, {longitude}'.format(latitude='37.24N', longitude='-115.81W')
'Coordinates: 37.24N, -115.81W'
>>> coord = {'latitude': '37.24N', 'longitude': '-115.81W'}
>>> 'Coordinates: {latitude}, {longitude}'.format(**coord)
'Coordinates: 37.24N, -115.81W'

>>> c = 3-5j
>>> ('The complex number {0} is formed from the real part {0.real} '
...  'and the imaginary part {0.imag}.').format(c)
'The complex number (3-5j) is formed from the real part 3.0 and the imaginary part -5.0.'
>>> class Point(object):
...     def __init__(self, x, y):
...         self.x, self.y = x, y
...     def __str__(self):
...         return 'Point({self.x}, {self.y})'.format(self=self)
...
>>> str(Point(4, 2))
'Point(4, 2)'

>>> coord = (3, 5)
>>> 'X: {0[0]};  Y: {0[1]}'.format(coord)
'X: 3;  Y: 5'

>>> "repr() shows quotes: {!r}; str() doesn't: {!s}".format('test1', 'test2')
"repr() shows quotes: 'test1'; str() doesn't: test2"

>>> '{:<30}'.format('left aligned')
'left aligned                  '
>>> '{:>30}'.format('right aligned')
'                 right aligned'
>>> '{:^30}'.format('centered')
'           centered           '
>>> '{:*^30}'.format('centered')  # use '*' as a fill char
'***********centered***********'

>>> '{:+f}; {:+f}'.format(3.14, -3.14)  # show it always
'+3.140000; -3.140000'
>>> '{: f}; {: f}'.format(3.14, -3.14)  # show a space for positive numbers
' 3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14)  # show only the minus -- same as '{:f}; {:f}'
'3.140000; -3.140000'

>>> # format also supports binary numbers
>>> "int: {0:d};  hex: {0:x};  oct: {0:o};  bin: {0:b}".format(42)
'int: 42;  hex: 2a;  oct: 52;  bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: {0:d};  hex: {0:#x};  oct: {0:#o};  bin: {0:#b}".format(42)
'int: 42;  hex: 0x2a;  oct: 0o52;  bin: 0b101010'

>>> '{:,}'.format(1234567890)
'1,234,567,890'

>>> points = 19.5
>>> total = 22
>>> 'Correct answers: {:.2%}'.format(points/total)
'Correct answers: 88.64%'

>>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'

>>> for align, text in zip('<^>', ['left', 'center', 'right']):
...     '{0:{fill}{align}16}'.format(text, fill=align, align=align)
...
'left<<<<<<<<<<<<'
'^^^^^center^^^^^'
'>>>>>>>>>>>right'
>>>
>>> octets = [192, 168, 0, 1]
>>> '{:02X}{:02X}{:02X}{:02X}'.format(*octets)
'C0A80001'
>>> int(_, 16)
3232235521
>>>
>>> width = 5
>>> for num in range(5,12):
...     for base in 'dXob':
...         print '{0:{width}{base}}'.format(num, base=base, width=width),
...     print
...
    5     5     5   101
    6     6     6   110
    7     7     7   111
    8     8    10  1000
    9     9    11  1001
   10     A    12  1010
   11     B    13  1011

Template strings

.. versionadded:: 2.4

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.

The :mod:`string` module provides a :class:`Template` class that implements these rules. The methods of :class:`Template` are:

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:: 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 $100').substitute(d)
Traceback (most recent call last):
...
ValueError: Invalid placeholder in string: line 1, col 11
>>> Template('$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 is $. 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[, sep])

   Split the argument into words using :meth:`str.split`, capitalize each word
   using :meth:`str.capitalize`, and join the capitalized words using
   :meth:`str.join`.  If the optional second argument *sep* is absent
   or ``None``, runs of whitespace characters are replaced by a single space
   and leading and trailing whitespace are removed, otherwise *sep* is used to
   split and join the words.

.. 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.

   .. note::

      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 :meth:`str.lower` and :meth:`str.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. 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.
   If *maxsplit* is given, 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).  If *maxsplit* is not
   specified or ``-1``, then there is no limit on the number of splits (all
   possible splits are made).

   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.  If *maxsplit* is given, 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[, fillchar])
              rjust(s, width[, fillchar])
              center(s, width[, fillchar])

   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 the character *fillchar*
   (default is a space) until the given width on the right, left or both sides.
   The string is never truncated.

.. function:: zfill(s, width)

   Pad a numeric string *s* on the left with zero digits until the
   given *width* is reached.  Strings starting with a sign are handled
   correctly.

.. function:: replace(s, old, new[, maxreplace])

   Return a copy of string *s* with all occurrences of substring *old* replaced
   by *new*.  If the optional argument *maxreplace* is given, the first
   *maxreplace* occurrences are replaced.