一点正则表达式:
import re
reg=re.compile('(\w+)[:=] ?"?(\w+)"?')
>>>dict(reg.findall(headers))
{'username': 'Foobear', 'realm': 'testrealm', 'qop': 'chap', 'cnonce': '5ccc069c403ebaf9f0171e9517f40e41', 'response': '6629fae49393a05397450978507c4ef1', 'Authorization': 'Digest'}