currently python behaves like this:
>>> import json
>>> a={'a': '//a[@asdf="asdf"]'}
>>> json.dumps(a)
'{"a": "//a[@asdf=\\"asdf\\"]"}'

this behaviour is incorrect.

the resulting string should be '{"a": "//a[@asdf=\"asdf\"]"}'

The difference is that double quotes inside double quotes are escaped twice instead of once. 

compare it to behaviour in javascript:

> var a = {'a': '//a[@asdf="asdf"]'}
undefined

JSON.stringify(a)
"{"a":"//a[@asdf=\"asdf\"]"}"

>>> print(json.dumps(a))
{"a": "//a[@asdf=\"asdf\"]"}

You seen the repr or the resulting string, not the resulting string itself.