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Patch by Jeffrey Chang to add docstrings everywhere. 

The text is condensed from the library manual.
This commit is contained in:
Guido van Rossum 1999-07-09 21:15:32 +00:00
parent 7c85ab829d
commit 6ebb387a08
1 changed files with 314 additions and 31 deletions
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345
Lib/re.py
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@ -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 @@ M = MULTILINE
S = DOTALL
X = VERBOSE
#
#
#
@ -37,33 +124,104 @@ def _cachecompile(pattern, flags=0):
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 @@ def escape(pattern):
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 @@ def compile(pattern, flags=0):
#
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 @@ class RegexObject:
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 @@ class RegexObject:
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 @@ class RegexObject:
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 @@ class RegexObject:
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 @@ class RegexObject:
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 @@ class _Dummy:
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 @@ class MatchObject:
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 @@ class MatchObject:
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 @@ class MatchObject:
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 @@ class MatchObject:
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 @@ class MatchObject:
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 @@ class MatchObject:
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]