re

Support for regular expressions (RE).

This module provides regular expression matching operations similar to
those found in Perl.  It supports both 8-bit and Unicode strings; both
the pattern and the strings being processed can contain null bytes and
characters outside the US ASCII range.

Regular expressions can contain both special and ordinary characters.
Most ordinary characters, like "A", "a", or "0", are the simplest
regular expressions; they simply match themselves.  You can
concatenate ordinary characters, so last matches the string 'last'.

The special characters are:
    "."      Matches any character except a newline.
    "^"      Matches the start of the string.
    "$"      Matches the end of the string or just before the newline at
             the end of the string.
    "*"      Matches 0 or more (greedy) repetitions of the preceding RE.
             Greedy means that it will match as many repetitions as possible.
    "+"      Matches 1 or more (greedy) repetitions of the preceding RE.
    "?"      Matches 0 or 1 (greedy) of the preceding RE.
    *?,+?,?? Non-greedy versions of the previous three special characters.
    {m,n}    Matches from m to n repetitions of the preceding RE.
    {m,n}?   Non-greedy version of the above.
    "\\"     Either escapes special characters or signals a special sequence.
    []       Indicates a set of characters.
             A "^" as the first character indicates a complementing set.
    "|"      A|B, creates an RE that will match either A or B.
    (...)    Matches the RE inside the parentheses.
             The contents can be retrieved or matched later in the string.
    (?aiLmsux) The letters set the corresponding flags defined below.
    (?:...)  Non-grouping version of regular parentheses.
    (?P<name>...) The substring matched by the group is accessible by name.
    (?P=name)     Matches the text matched earlier by the group named name.
    (?#...)  A comment; ignored.
    (?=...)  Matches if ... matches next, but doesn't consume the string.
    (?!...)  Matches if ... doesn't match next.
    (?<=...) Matches if preceded by ... (must be fixed length).
    (?<!...) Matches if not preceded by ... (must be fixed length).
    (?(id/name)yes|no) Matches yes pattern if the group with id/name matched,
                       the (optional) no pattern otherwise.

The special sequences consist of "\\" and a character from the list
below.  If the ordinary character is not on the list, then the
resulting RE will match the second character.
    \number  Matches the contents of the group of the same number.
    \A       Matches only at the start of the string.
    \Z       Matches only at the end of the string.
    \b       Matches the empty string, but only at the start or end of a word.
    \B       Matches the empty string, but not at the start or end of a word.
    \d       Matches any decimal digit; equivalent to the set [0-9] in
             bytes patterns or string patterns with the ASCII flag.
             In string patterns without the ASCII flag, it will match the whole
             range of Unicode digits.
    \D       Matches any non-digit character; equivalent to [^\d].
    \s       Matches any whitespace character; equivalent to [ \t\n\r\f\v] in
             bytes patterns or string patterns with the ASCII flag.
             In string patterns without the ASCII flag, it will match the whole
             range of Unicode whitespace characters.
    \S       Matches any non-whitespace character; equivalent to [^\s].
    \w       Matches any alphanumeric character; equivalent to [a-zA-Z0-9_]
             in bytes patterns or string patterns with the ASCII flag.
             In string patterns without the ASCII flag, it will match the
             range of Unicode alphanumeric characters (letters plus digits
             plus underscore).
             With LOCALE, it will match the set [0-9_] plus characters defined
             as letters for the current locale.
    \W       Matches the complement of \w.
    \\       Matches a literal backslash.

This module exports the following functions:
    match     Match a regular expression pattern to the beginning of a string.
    fullmatch Match a regular expression pattern to all of a string.
    search    Search a string for the presence of a pattern.
    sub       Substitute occurrences of a pattern found in a string.
    subn      Same as sub, but also return the number of substitutions made.
    split     Split a string by the occurrences of a pattern.
    findall   Find all occurrences of a pattern in a string.
    finditer  Return an iterator yielding a Match object for each match.
    compile   Compile a pattern into a Pattern object.
    purge     Clear the regular expression cache.
    escape    Backslash all non-alphanumerics in a string.

Each function other than purge and escape can take an optional 'flags' argument
consisting of one or more of the following module constants, joined by "|".
A, L, and U are mutually exclusive.
    A  ASCII       For string patterns, make \w, \W, \b, \B, \d, \D
                   match the corresponding ASCII character categories
                   (rather than the whole Unicode categories, which is the
                   default).
                   For bytes patterns, this flag is the only available
                   behaviour and needn't be specified.
    I  IGNORECASE  Perform case-insensitive matching.
    L  LOCALE      Make \w, \W, \b, \B, dependent on the current locale.
    M  MULTILINE   "^" matches the beginning of lines (after a newline)
                   as well as the string.
                   "$" matches the end of lines (before a newline) as well
                   as the end of the string.
    S  DOTALL      "." matches any character at all, including the newline.
    X  VERBOSE     Ignore whitespace and comments for nicer looking RE's.
    U  UNICODE     For compatibility only. Ignored for string patterns (it
                   is the default), and forbidden for bytes patterns.

This module also defines an exception 'error'.

Classes

Match

The result of re.match() and re.search().
Match objects always have a boolean value of True.

end(self, group=0, /)

  Return index of the end of the substring matched by group.

expand(self, /, template)

  Return the string obtained by doing backslash substitution on the string template, as done by the sub() method.

group(...)

  group([group1, ...]) -> str or tuple.
      Return subgroup(s) of the match by indices or names.
      For 0 returns the entire match.

groupdict(self, /, default=None)

  Return a dictionary containing all the named subgroups of the match, keyed by the subgroup name.

    default
      Is used for groups that did not participate in the match.

groups(self, /, default=None)

  Return a tuple containing all the subgroups of the match, from 1.

    default
      Is used for groups that did not participate in the match.

span(self, group=0, /)

  For match object m, return the 2-tuple (m.start(group), m.end(group)).

start(self, group=0, /)

  Return index of the start of the substring matched by group.

endpos = <member 'endpos' of 're.Match' objects>
  The index into the string beyond which the RE engine will not go.

lastgroup = <attribute 'lastgroup' of 're.Match' objects>
  The name of the last matched capturing group.

lastindex = <attribute 'lastindex' of 're.Match' objects>
  The integer index of the last matched capturing group.

pos = <member 'pos' of 're.Match' objects>
  The index into the string at which the RE engine started looking for a match.

re = <member 're' of 're.Match' objects>
  The regular expression object.

regs = <attribute 'regs' of 're.Match' objects>

string = <member 'string' of 're.Match' objects>
  The string passed to match() or search().

Pattern

Compiled regular expression object.

findall(self, /, string, pos=0, endpos=9223372036854775807)

  Return a list of all non-overlapping matches of pattern in string.

finditer(self, /, string, pos=0, endpos=9223372036854775807)

  Return an iterator over all non-overlapping matches for the RE pattern in string.

  For each match, the iterator returns a match object.

fullmatch(self, /, string, pos=0, endpos=9223372036854775807)

  Matches against all of the string.

match(self, /, string, pos=0, endpos=9223372036854775807)

  Matches zero or more characters at the beginning of the string.

scanner(self, /, string, pos=0, endpos=9223372036854775807)

search(self, /, string, pos=0, endpos=9223372036854775807)

  Scan through string looking for a match, and return a corresponding match object instance.

  Return None if no position in the string matches.

split(self, /, string, maxsplit=0)

  Split string by the occurrences of pattern.

sub(self, /, repl, string, count=0)

  Return the string obtained by replacing the leftmost non-overlapping occurrences of pattern in string by the replacement repl.

subn(self, /, repl, string, count=0)

  Return the tuple (new_string, number_of_subs_made) found by replacing the leftmost non-overlapping occurrences of pattern with the replacement repl.

flags = <member 'flags' of 're.Pattern' objects>
  The regex matching flags.

groupindex = <attribute 'groupindex' of 're.Pattern' objects>
  A dictionary mapping group names to group numbers.

groups = <member 'groups' of 're.Pattern' objects>
  The number of capturing groups in the pattern.

pattern = <member 'pattern' of 're.Pattern' objects>
  The pattern string from which the RE object was compiled.

RegexFlag

An enumeration.

ASCII = re.ASCII

DEBUG = re.DEBUG

DOTALL = re.DOTALL

IGNORECASE = re.IGNORECASE

LOCALE = re.LOCALE

MULTILINE = re.MULTILINE

TEMPLATE = re.TEMPLATE

UNICODE = re.UNICODE

VERBOSE = re.VERBOSE

Scanner

scan(self, string)

error

Exception raised for invalid regular expressions.

    Attributes:

        msg: The unformatted error message
        pattern: The regular expression pattern
        pos: The index in the pattern where compilation failed (may be None)
        lineno: The line corresponding to pos (may be None)
        colno: The column corresponding to pos (may be None)

with_traceback(...)

  Exception.with_traceback(tb) --
      set self.__traceback__ to tb and return self.

args = <attribute 'args' of 'BaseException' objects>

Functions

compile

compile(pattern, flags=0)

  Compile a regular expression pattern, returning a Pattern object.

escape

escape(pattern)


      Escape special characters in a string.

findall

findall(pattern, string, flags=0)

  Return a list of all non-overlapping matches in the string.

      If one or more capturing groups are present in the pattern, return
      a list of groups; this will be a list of tuples if the pattern
      has more than one group.

      Empty matches are included in the result.

finditer

finditer(pattern, string, flags=0)

  Return an iterator over all non-overlapping matches in the
      string.  For each match, the iterator returns a Match object.

      Empty matches are included in the result.

fullmatch

fullmatch(pattern, string, flags=0)

  Try to apply the pattern to all of the string, returning
      a Match object, or None if no match was found.

match

match(pattern, string, flags=0)

  Try to apply the pattern at the start of the string, returning
      a Match object, or None if no match was found.

purge

purge()

  Clear the regular expression caches

search

search(pattern, string, flags=0)

  Scan through string looking for a match to the pattern, returning
      a Match object, or None if no match was found.

split

split(pattern, string, maxsplit=0, flags=0)

  Split the source string by the occurrences of the pattern,
      returning a list containing the resulting substrings.  If
      capturing parentheses are used in pattern, then the text of all
      groups in the pattern are also returned as part of the resulting
      list.  If maxsplit is nonzero, at most maxsplit splits occur,
      and the remainder of the string is returned as the final element
      of the list.

sub

sub(pattern, repl, string, count=0, flags=0)

  Return the string obtained by replacing the leftmost
      non-overlapping occurrences of the pattern in string by the
      replacement repl.  repl can be either a string or a callable;
      if a string, backslash escapes in it are processed.  If it is
      a callable, it's passed the Match object and must return
      a replacement string to be used.

subn

subn(pattern, repl, string, count=0, flags=0)

  Return a 2-tuple containing (new_string, number).
      new_string is the string obtained by replacing the leftmost
      non-overlapping occurrences of the pattern in the source
      string by the replacement repl.  number is the number of
      substitutions that were made. repl can be either a string or a
      callable; if a string, backslash escapes in it are processed.
      If it is a callable, it's passed the Match object and must
      return a replacement string to be used.

template

template(pattern, flags=0)

  Compile a template pattern, returning a Pattern object

Other members

A = re.ASCII

ASCII = re.ASCII

DEBUG = re.DEBUG

DOTALL = re.DOTALL

I = re.IGNORECASE

IGNORECASE = re.IGNORECASE

L = re.LOCALE

LOCALE = re.LOCALE

M = re.MULTILINE

MULTILINE = re.MULTILINE

S = re.DOTALL

T = re.TEMPLATE

TEMPLATE = re.TEMPLATE

U = re.UNICODE

UNICODE = re.UNICODE

VERBOSE = re.VERBOSE

X = re.VERBOSE

Modules