Python正则表达式在替换中使用Match作为Dict键

我正在将一个程序从Perl翻译成Python（3.3）。我对Python相当陌生。在Perl中，我可以进行巧妙的正则表达式替换，例如：

$string =~ s/<(\w+)>/$params->{$1}/g;

如果我可以传递一个将正则表达式匹配映射到dict的函数，那可能会更好。这可能吗

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谢谢您的帮助。

您可以将一个可调用的消息传递给

re.sub

，告诉它如何处理匹配对象

s = re.sub(r'<(\w+)>', lambda m: replacement_dict.get(m.group()), s)

我要注意的是，当使用

re.sub

（和family，即

re.split

）时，当指定存在于所需替换周围的内容时，使用lookaround表达式通常更为简洁，这样匹配周围的内容就不会被分包出去。所以在这种情况下，我会像这样写你的正则表达式

r'(?<=<)(\w+)(?=>)'

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很好，这解决了我的问题。谢谢你的详细解释。

lambda m: replacement_dict.get(m.group(), m.group()) 
# fallback to just leaving the word there if we don't have a replacement

r'(?<=<)(\w+)(?=>)'

s = "<sometag>this is stuff<othertag>this is other stuff<closetag>"

d = {'othertag': 'blah'}

#this doesn't work because `group` returns the whole match, including non-groups
re.sub(r'<(\w+)>', lambda m: d.get(m.group(), m.group()), s)
Out[23]: '<sometag>this is stuff<othertag>this is other stuff<closetag>'

#this output isn't exactly ideal...
re.sub(r'<(\w+)>', lambda m: d.get(m.group(1), m.group(1)), s)
Out[24]: 'sometagthis is stuffblahthis is other stuffclosetag'

#this works, but is ugly and hard to maintain
re.sub(r'<(\w+)>', lambda m: '<{}>'.format(d.get(m.group(1), m.group(1))), s)
Out[26]: '<sometag>this is stuff<blah>this is other stuff<closetag>'

#lookbehind/lookahead makes this nicer.
re.sub(r'(?<=<)(\w+)(?=>)', lambda m: d.get(m.group(), m.group()), s)
Out[27]: '<sometag>this is stuff<blah>this is other stuff<closetag>'