Pythonic way to parse a formatted string and get a dictionary out of it

Question

I have a string that looks like this:

{
    "key A":[
        ["some val", "value a1"],
        ["some val", "value a2"],
        ....................
        ["some val", "value an"]
    ], "key B":[
        ["some val", "value b1"],
        ["some val", "value b2"],
        ...
    ], ...
     , "key X":[
        ["some val", "value x1"],
        ["some val", "value x2"],
        ...
    ]
}

Can anyone tell me what is the proper way in python to get a dictionary out of it where the dictionary should be

{
    "key A": ["val a1", "val a2", ..."val an"],
    "key B": ["val b1", "val b2", ..."val bn"],
    .....
    "key X": ["val x1", "val x2", ..."val xn"],
}

I'm asking this because right now the only code I can think of is a pretty dirty one with a lot of list, splits and replaces and I'm quite sure that this is very wrong way to do it :D. Thanks a lot in advance.

Answer 1

You can use ast.literal_eval with a dictionary comprehension:

from ast import literal_eval

mystr = """{
    "key A":[
        ["some val", "value a1"],
        ["some val", "value a2"],
        ["some val", "value an"]
    ], "key B":[
        ["some val", "value b1"],
        ["some val", "value b2"],
    ], "key X":[
        ["some val", "value x1"],
        ["some val", "value x2"],
    ]
}"""

res = {k: list(list(zip(*v))[1]) for k, v in literal_eval(mystr).items()}

# {'key A': ['value a1', 'value a2', 'value an'],
#  'key B': ['value b1', 'value b2'],
#  'key X': ['value x1', 'value x2']}

Answer 2

As eval is generally regarded as unsafe and python dictionaries are "usually" JSON compatible, as long as all values are also JSON compatible. I would recommend:

import json

mystr = """{
    "key A":[
        ["some val", "value a1"],
        ["some val", "value a2"],
        ["some val", "value an"]
    ], "key B":[
        ["some val", "value b1"],
        ["some val", "value b2"]
    ], "key X":[
        ["some val", "value x1"],
        ["some val", "value x2"]
    ]
}"""

res = json.loads(mystr)

for dealing with trailing commas:

import json
from jsoncomment import JsonComment


mystr = """{
    "key A":[
        ["some val", "value a1"],
        ["some val", "value a2"],
        ["some val", "value an"]
    ], "key B":[
        ["some val", "value b1"],
        ["some val", "value b2"],
    ], "key X":[
        ["some val", "value x1"],
        ["some val", "value x2"],
    ]
}"""

res = JsonComment(json).loads(mystr)

docs for JsonComment: https://pypi.python.org/pypi/jsoncomment

ref: Can json.loads ignore trailing commas?