Patch by Jeffrey Chang to add docstrings everywhere.
The text is condensed from the library manual.
diff --git a/Lib/re.py b/Lib/re.py
index d190363..8f6bc5f 100644
--- a/Lib/re.py
+++ b/Lib/re.py
@@ -1,3 +1,89 @@
+# module 're' -- A collection of regular expression operations
+
+"""Support for regular expressions (RE).
+
+This module provides regular expression matching operations similar to
+those found in Perl. It's 8-bit clean: the strings being processed may
+contain both null bytes and characters whose high bit is set. Regular
+expression pattern strings may not contain null bytes, but can specify
+the null byte using the \\number notation. Characters with the high
+bit set may be included.
+
+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.
+ "*" Matches 0 or more (greedy) repetitions of the preceding RE.
+ Greedy means that it will match as many repetitions as possible.
+ "+" Matches 0 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.
+ (?iLmsx) Set the I, L, M, S, or X flag for the RE.
+ (?:...) 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.
+
+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].
+ \\D Matches any non-digit character; equivalent to the set [^0-9].
+ \\s Matches any whitespace character; equivalent to [ \\t\\n\\r\\f\\v].
+ \\S Matches any non-whitespace character; equiv. to [^ \\t\\n\\r\\f\\v].
+ \\w Matches any alphanumeric character; equivalent to [a-zA-Z0-9_].
+ 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.
+ 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.
+ compile Compile a pattern into a RegexObject.
+ escape Backslash all non-alphanumerics in a string.
+
+This module exports the following classes:
+ RegexObject Holds a compiled regular expression pattern.
+ MatchObject Contains information about pattern matches.
+
+Some of the functions in this module takes flags as optional parameters:
+ 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 as well as the string.
+ "$" matches the end of lines as well as the string.
+ S DOTALL "." matches any character at all, including the newline.
+ X VERBOSE Ignore whitespaces and comments for nicer looking RE's.
+
+This module also defines an exception 'error'.
+
+"""
+
+
import sys
import string
from pcre import *
@@ -17,6 +103,7 @@
S = DOTALL
X = VERBOSE
+
#
#
#
@@ -37,33 +124,104 @@
return value
def match(pattern, string, flags=0):
+ """match (pattern, string[, flags]) -> MatchObject or None
+
+ If zero or more characters at the beginning of string match the
+ regular expression pattern, return a corresponding MatchObject
+ instance. Return None if the string does not match the pattern;
+ note that this is different from a zero-length match.
+
+ Note: If you want to locate a match anywhere in string, use
+ search() instead.
+
+ """
+
return _cachecompile(pattern, flags).match(string)
def search(pattern, string, flags=0):
+ """search (pattern, string[, flags]) -> MatchObject or None
+
+ Scan through string looking for a location where the regular
+ expression pattern produces a match, and return a corresponding
+ MatchObject instance. Return None if no position in the string
+ matches the pattern; note that this is different from finding a
+ zero-length match at some point in the string.
+
+ """
return _cachecompile(pattern, flags).search(string)
def sub(pattern, repl, string, count=0):
+ """sub(pattern, repl, string[, count=0]) -> string
+
+ Return the string obtained by replacing the leftmost
+ non-overlapping occurrences of pattern in string by the
+ replacement repl. If the pattern isn't found, string is returned
+ unchanged. repl can be a string or a function; if a function, it
+ is called for every non-overlapping occurrence of pattern. The
+ function takes a single match object argument, and returns the
+ replacement string.
+
+ The pattern may be a string or a regex object; if you need to
+ specify regular expression flags, you must use a regex object, or
+ use embedded modifiers in a pattern; e.g.
+ sub("(?i)b+", "x", "bbbb BBBB") returns 'x x'.
+
+ The optional argument count is the maximum number of pattern
+ occurrences to be replaced; count must be a non-negative integer,
+ and the default value of 0 means to replace all occurrences.
+
+ """
if type(pattern) == type(''):
pattern = _cachecompile(pattern)
return pattern.sub(repl, string, count)
def subn(pattern, repl, string, count=0):
+ """subn(pattern, repl, string[, count=0]) -> (string, num substitutions)
+
+ Perform the same operation as sub(), but return a tuple
+ (new_string, number_of_subs_made).
+
+ """
if type(pattern) == type(''):
pattern = _cachecompile(pattern)
return pattern.subn(repl, string, count)
def split(pattern, string, maxsplit=0):
+ """split(pattern, string[, maxsplit=0]) -> list of strings
+
+ Split string by the occurrences of pattern. 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.
+
+ """
if type(pattern) == type(''):
pattern = _cachecompile(pattern)
return pattern.split(string, maxsplit)
def findall(pattern, string):
+ """findall(pattern, string) -> list
+
+ Return a list of all non-overlapping matches of pattern in
+ string. If one or more 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.
+
+ """
if type(pattern) == type(''):
pattern = _cachecompile(pattern)
return pattern.findall(string)
def escape(pattern):
- "Escape all non-alphanumeric characters in pattern."
+ """escape(string) -> string
+
+ Return string with all non-alphanumerics backslashed; this is
+ useful if you want to match an arbitrary literal string that may
+ have regular expression metacharacters in it.
+
+ """
result = list(pattern)
alphanum=string.letters+'_'+string.digits
for i in range(len(pattern)):
@@ -74,7 +232,13 @@
return string.join(result, '')
def compile(pattern, flags=0):
- "Compile a regular expression pattern, returning a RegexObject."
+ """compile(pattern[, flags]) -> RegexObject
+
+ Compile a regular expression pattern into a regular expression
+ object, which can be used for matching using its match() and
+ search() methods.
+
+ """
groupindex={}
code=pcre_compile(pattern, flags, groupindex)
return RegexObject(pattern, flags, code, groupindex)
@@ -85,6 +249,17 @@
#
class RegexObject:
+ """Holds a compiled regular expression pattern.
+
+ Methods:
+ match Match the pattern to the beginning of a string.
+ search Search a string for the presence of the pattern.
+ sub Substitute occurrences of the 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 the pattern.
+ findall Find all occurrences of the pattern in a string.
+
+ """
def __init__(self, pattern, flags, code, groupindex):
self.code = code
@@ -93,9 +268,17 @@
self.groupindex = groupindex
def search(self, string, pos=0, endpos=None):
- """Scan through string looking for a match to the pattern, returning
- a MatchObject instance, or None if no match was found."""
-
+ """search(string[, pos][, endpos]) -> MatchObject or None
+
+ Scan through string looking for a location where this regular
+ expression produces a match, and return a corresponding
+ MatchObject instance. Return None if no position in the string
+ matches the pattern; note that this is different from finding
+ a zero-length match at some point in the string. The optional
+ pos and endpos parameters have the same meaning as for the
+ match() method.
+
+ """
if endpos is None or endpos>len(string):
endpos=len(string)
if endpos<pos: endpos=pos
@@ -110,9 +293,29 @@
regs)
def match(self, string, pos=0, endpos=None):
- """Try to apply the pattern at the start of the string, returning
- a MatchObject instance, or None if no match was found."""
+ """match(string[, pos][, endpos]) -> MatchObject or None
+
+ If zero or more characters at the beginning of string match
+ this regular expression, return a corresponding MatchObject
+ instance. Return None if the string does not match the
+ pattern; note that this is different from a zero-length match.
+ Note: If you want to locate a match anywhere in string, use
+ search() instead.
+
+ The optional second parameter pos gives an index in the string
+ where the search is to start; it defaults to 0. This is not
+ completely equivalent to slicing the string; the '' pattern
+ character matches at the real beginning of the string and at
+ positions just after a newline, but not necessarily at the
+ index where the search is to start.
+
+ The optional parameter endpos limits how far the string will
+ be searched; it will be as if the string is endpos characters
+ long, so only the characters from pos to endpos will be
+ searched for a match.
+
+ """
if endpos is None or endpos>len(string):
endpos=len(string)
if endpos<pos: endpos=pos
@@ -126,19 +329,25 @@
regs)
def sub(self, repl, string, count=0):
- """Return the string obtained by replacing the leftmost
- non-overlapping occurrences of the pattern in string by the
- replacement repl"""
+ """sub(repl, string[, count=0]) -> string
+
+ Return the string obtained by replacing the leftmost
+ non-overlapping occurrences of the compiled pattern in string
+ by the replacement repl. If the pattern isn't found, string is
+ returned unchanged.
+ Identical to the sub() function, using the compiled pattern.
+
+ """
return self.subn(repl, string, count)[0]
def subn(self, repl, source, count=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."""
+ """subn(repl, string[, count=0]) -> tuple
+ Perform the same operation as sub(), but return a tuple
+ (new_string, number_of_subs_made).
+
+ """
if count < 0:
raise error, "negative substitution count"
if count == 0:
@@ -192,9 +401,16 @@
return (string.join(results, ''), n)
def split(self, source, maxsplit=0):
- """Split the source string by the occurrences of the pattern,
- returning a list containing the resulting substrings."""
-
+ """split(source[, maxsplit=0]) -> list of strings
+
+ Split string by the occurrences of the compiled pattern. If
+ capturing parentheses are used in the 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.
+
+ """
if maxsplit < 0:
raise error, "negative split count"
if maxsplit == 0:
@@ -232,13 +448,13 @@
return results
def findall(self, source):
- """Return a list of all non-overlapping matches in the string.
-
- If one or more 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.
+ """findall(source) -> list
+
+ Return a list of all non-overlapping matches of the compiled
+ pattern in string. If one or more 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.
"""
pos = 0
@@ -286,6 +502,17 @@
group = None
class MatchObject:
+ """Holds a compiled regular expression pattern.
+
+ Methods:
+ start Return the index of the start of a matched substring.
+ end Return the index of the end of a matched substring.
+ span Return a tuple of (start, end) of a matched substring.
+ groups Return a tuple of all the subgroups of the match.
+ group Return one or more subgroups of the match.
+ groupdict Return a dictionary of all the named subgroups of the match.
+
+ """
def __init__(self, re, string, pos, endpos, regs):
self.re = re
@@ -295,7 +522,14 @@
self.regs = regs
def start(self, g = 0):
- "Return the start of the substring matched by group g"
+ """start([group=0]) -> int or None
+
+ Return the index of the start of the substring matched by
+ group; group defaults to zero (meaning the whole matched
+ substring). Return None if group exists but did not contribute
+ to the match.
+
+ """
if type(g) == type(''):
try:
g = self.re.groupindex[g]
@@ -304,7 +538,14 @@
return self.regs[g][0]
def end(self, g = 0):
- "Return the end of the substring matched by group g"
+ """end([group=0]) -> int or None
+
+ Return the indices of the end of the substring matched by
+ group; group defaults to zero (meaning the whole matched
+ substring). Return None if group exists but did not contribute
+ to the match.
+
+ """
if type(g) == type(''):
try:
g = self.re.groupindex[g]
@@ -313,7 +554,14 @@
return self.regs[g][1]
def span(self, g = 0):
- "Return (start, end) of the substring matched by group g"
+ """span([group=0]) -> tuple
+
+ Return the 2-tuple (m.start(group), m.end(group)). Note that
+ if group did not contribute to the match, this is (None,
+ None). Group defaults to zero (meaning the whole matched
+ substring).
+
+ """
if type(g) == type(''):
try:
g = self.re.groupindex[g]
@@ -322,7 +570,14 @@
return self.regs[g]
def groups(self, default=None):
- "Return a tuple containing all subgroups of the match object"
+ """groups([default=None]) -> tuple
+
+ Return a tuple containing all the subgroups of the match, from
+ 1 up to however many groups are in the pattern. The default
+ argument is used for groups that did not participate in the
+ match.
+
+ """
result = []
for g in range(1, self.re._num_regs):
a, b = self.regs[g]
@@ -333,7 +588,29 @@
return tuple(result)
def group(self, *groups):
- "Return one or more groups of the match"
+ """group([group1, group2, ...]) -> string or tuple
+
+ Return one or more subgroups of the match. If there is a
+ single argument, the result is a single string; if there are
+ multiple arguments, the result is a tuple with one item per
+ argument. Without arguments, group1 defaults to zero (i.e. the
+ whole match is returned). If a groupN argument is zero, the
+ corresponding return value is the entire matching string; if
+ it is in the inclusive range [1..99], it is the string
+ matching the the corresponding parenthesized group. If a group
+ number is negative or larger than the number of groups defined
+ in the pattern, an IndexError exception is raised. If a group
+ is contained in a part of the pattern that did not match, the
+ corresponding result is None. If a group is contained in a
+ part of the pattern that matched multiple times, the last
+ match is returned.
+
+ If the regular expression uses the (?P<name>...) syntax, the
+ groupN arguments may also be strings identifying groups by
+ their group name. If a string argument is not used as a group
+ name in the pattern, an IndexError exception is raised.
+
+ """
if len(groups) == 0:
groups = (0,)
result = []
@@ -358,7 +635,13 @@
return ()
def groupdict(self, default=None):
- "Return a dictionary containing all named subgroups of the match"
+ """groupdict([default=None]) -> dictionary
+
+ Return a dictionary containing all the named subgroups of the
+ match, keyed by the subgroup name. The default argument is
+ used for groups that did not participate in the match.
+
+ """
dict = {}
for name, index in self.re.groupindex.items():
a, b = self.regs[index]