大约一年前我从Perl切换到Python，并没有回头。只有一个成语，我发现我可以在Perl比在Python更容易做到：
if ($var =~ /foo(.+)/) {
# do something with $1
} elsif ($var =~ /bar(.+)/) {
# do something with $1
} elsif ($var =~ /baz(.+)/) {
# do something with $1
}
相应的Python代码不那么优雅，因为if语句继续嵌套：
m = re.search(r'foo(.+)',var)
if m:
# do something with m.group(1)
else:
m = re.search(r'bar(.+)',var)
if m:
# do something with m.group(1)
else:
m = re.search(r'baz(.+)',var)
if m:
# do something with m.group(2)
有没有人有一个优雅的方式来重现这种模式在Python？我看过使用的匿名函数调度表，但是对于少量的正则表达式，这些表似乎对我来说是不方便的。
r"""
This is an extension of the re module. It stores the last successful
match object and lets you access it's methods and attributes via
this module.
This module exports the following additional functions:
expand Return the string obtained by doing backslash substitution on a
template string.
group Returns one or more subgroups of the match.
groups Return a tuple containing all the subgroups of the match.
start Return the indices of the start of the substring matched by
group.
end Return the indices of the end of the substring matched by group.
span Returns a 2-tuple of (start(),end()) of the substring matched
by group.
This module defines the following additional public attributes:
pos The value of pos which was passed to the search() or match()
method.
endpos The value of endpos which was passed to the search() or
match() method.
lastindex The integer index of the last matched capturing group.
lastgroup The name of the last matched capturing group.
re The regular expression object which as passed to search() or
match().
string The string passed to match() or search().
"""
import re as re_
from re import *
from functools import wraps
__all__ = re_.__all__ + [ "expand","group","groups","start","end","span","last_match","pos","endpos","lastindex","lastgroup","re","string" ]
last_match = pos = endpos = lastindex = lastgroup = re = string = None
def _set_match(match=None):
global last_match,pos,endpos,lastindex,lastgroup,re,string
if match is not None:
last_match = match
pos = match.pos
endpos = match.endpos
lastindex = match.lastindex
lastgroup = match.lastgroup
re = match.re
string = match.string
return match
@wraps(re_.match)
def match(pattern,string,flags=0):
return _set_match(re_.match(pattern,flags))
@wraps(re_.search)
def search(pattern,flags=0):
return _set_match(re_.search(pattern,flags))
@wraps(re_.findall)
def findall(pattern,flags=0):
matches = re_.findall(pattern,flags)
if matches:
_set_match(matches[-1])
return matches
@wraps(re_.finditer)
def finditer(pattern,flags=0):
for match in re_.finditer(pattern,flags):
yield _set_match(match)
def expand(template):
if last_match is None:
raise TypeError,"No successful match yet."
return last_match.expand(template)
def group(*indices):
if last_match is None:
raise TypeError,"No successful match yet."
return last_match.group(*indices)
def groups(default=None):
if last_match is None:
raise TypeError,"No successful match yet."
return last_match.groups(default)
def groupdict(default=None):
if last_match is None:
raise TypeError,"No successful match yet."
return last_match.groupdict(default)
def start(group=0):
if last_match is None:
raise TypeError,"No successful match yet."
return last_match.start(group)
def end(group=0):
if last_match is None:
raise TypeError,"No successful match yet."
return last_match.end(group)
def span(group=0):
if last_match is None:
raise TypeError,"No successful match yet."
return last_match.span(group)
del wraps # Not needed past module compilation
例如：
if gre.match("foo(.+)",var):
# do something with gre.group(1)
elif gre.match("bar(.+)",var):
# do something with gre.group(1)
elif gre.match("baz(.+)",var):
# do something with gre.group(1)
