Why doesn't json.loads('{"Testing": "This quo\\\\"te String"}-CodePudding

I'm trying to understand why the code below doesn't work in Python:

import json

s = json.loads(' {"Testing" : "This quo\\\\"te String"} ')

print(s)

Theoretically, what I should get back is {'Testing' : 'This quo\"te String'}.

These ones work fine:

print(json.loads(' {"Testing" : "This quo\\"te String"} ')) ----> {'Testing' : 'This quo"te String'}

print(json.loads(' {"Testing" :"This quo\\\\\\"te String"}')) ----> {'Testing' : 'This quo\\"te String'}

I'm guessing it has something to do with the Idiosyncrasy of having a \" in the dict, but can't figure out what exactly is happening.

CodePudding user response：

You need an odd number of pairs of backslashes in your python string to end up with an odd number of backslashes in the json. Each pair of backslashes then becomes a single backslash and you need one more -- the odd one -- to escape the quote mark.

CodePudding user response：

The string This quo\"te String requires two escapes in normal Python: one for the \ and one for the ", making three backslashes in all:

>>> print("This quo\\\"te String")
This quo\"te String

For json, all those backslashes must be themselves escaped, because the string is embedded inside another string. Thus, six backslashes are required in total:

>>> print(json.loads('"This quo\\\\\\"te String"'))
This quo\"te String

However, if raw-strings are used, no extra escapes are required:

>>> print(json.loads(r'"This quo\\\"te String"'))
This quo\"te String

In your first example, the four backslashes will be parsed as a single literal \ (i.e. as an escaped backslash), leaving the " unescaped.

Note that it makes no difference if the string is inside a dict - the result will be exactly the same:

>>> dct = json.loads('{"Testing": "This quo\\\\\\"te String"}')
>>> print(dct['Testing'])
This quo\"te String