Python-сообщество

s = s.replace('&', '&')

from html.parser import HTMLParser # python 3
from HTMLParser import HTMLParser # python 2
HTMLParser().unescape(s)

>>> import html.entities
>>> html.entities.entitydefs['amp']
'&'
>>>

In [2]: HTMLParser.unescape?
Type:       instancemethod
Base Class: <type 'instancemethod'>
String Form:<unbound method HTMLParser.unescape>
Namespace:  Interactive
File:       /usr/lib/python2.7/HTMLParser.py
Definition: HTMLParser.unescape(self, s)
Docstring:  <no docstring>
In [3]: %psource HTMLParser.unescape
    def unescape(self, s):
        if '&' not in s:
            return s
        def replaceEntities(s):
            s = s.groups()[0]
            try:
                if s[0] == "#":
                    s = s[1:]
                    if s[0] in ['x','X']:
                        c = int(s[1:], 16)
                    else:
                        c = int(s)
                    return unichr(c)
            except ValueError:
                return '&#'+s+';'
            else:
                # Cannot use name2codepoint directly, because HTMLParser supports apos,
                # which is not part of HTML 4
                import htmlentitydefs
                if HTMLParser.entitydefs is None:
                    entitydefs = HTMLParser.entitydefs = {'apos':u"'"}
                    for k, v in htmlentitydefs.name2codepoint.iteritems():
                        entitydefs[k] = unichr(v)
                try:
                    return self.entitydefs[s]
                except KeyError:
                    return '&'+s+';'
        return re.sub(r"&(#?[xX]?(?:[0-9a-fA-F]+|\w{1,8}));", replaceEntities, s)

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