how to parse a string into a dictionary

Question

I am trying to parse a string to separate the lists within the string. I currently have the string:

string = \"[[\'q1\', \'0\', \'q1\'], [\'q1\', \'1\', \'q2         


        

Answer 1

You can use JSON but the string format has to be a dict and you cannot have 2 times the same key:

import json

string ='{"q": ["0", "q1"], "q1": ["1", "q2"], "q3": ["1", "q1"], "q2": ["0", "q2"]}'

dict = json.loads(string)

print dict
Output: {'q': ['0', 'q1'], 'q1': ['1', 'q2'], 'q3': ['1', 'q1'], 'q2': ['0', 'q2']}

Answer 2

try this

>>> import ast
>>> ast.literal_eval(string)
[['q1', '0', 'q1'], ['q1', '1', 'q2'], ['q2', '0', 'q2'], ['q2', '1', 'q1']]
>>> list=ast.literal_eval(string)
>>> d={}
>>> for l in list:
...     d[l[0]]=tuple(l[1:])
>>> d
{'q1': ('1', 'q2'), 'q2': ('1', 'q1')}

key is always unique in dict thats why in result showing updated key value pair

Answer 3

To keep the duplicates and conform the input format:

import collections
import json
string = "[['q1', '0', 'q1'], ['q1', '1', 'q2'], ['q2', '0', 'q2'], ['q2', '1', 'q1']]"
d = collections.defaultdict(list)
for (k, v1, v2) in json.loads(string.replace("'",'"')):
    d[k].append((v1, v2))

With eval (if you trust your input):

import collections
string = "[['q1', '0', 'q1'], ['q1', '1', 'q2'], ['q2', '0', 'q2'], ['q2', '1', 'q1']]"
d = collections.defaultdict(list)
for (k, v1, v2) in eval(string):
    d[k].append((v1, v2))

Contents of d:

defaultdict(<type 'list'>, {
    'q1': [('0', 'q1'), ('1', 'q2')],
    'q2': [('0', 'q2'), ('1', 'q1')]
})

EDIT: and with no library at all.

string = "[['q1', '0', 'q1'], ['q1', '1', 'q2'], ['q2', '0', 'q2'], ['q2', '1', 'q1']]"
d = {}
for (k, v1, v2) in eval(string):
    d.setdefault(k, []).append((v1, v2))

I'm unable to make it a one-liner though :-)

Answer 4

Insted of dictionary you can have list:
you can use ast.literal_eval to parse python data structure from string

>>> import ast
>>> my_string = "[['q1', '0', 'q1'], ['q1', '1', 'q2'], ['q2', '0', 'q2'], ['q2', '1', 'q1']]"
>>> k = ast.literal_eval(my_string)
>>> k
[['q1', '0', 'q1'], ['q1', '1', 'q2'], ['q2', '0', 'q2'], ['q2', '1', 'q1']]
>>> [[x[0],tuple(x[1:])] for x in k]
[['q1', ('0', 'q1')], ['q1', ('1', 'q2')], ['q2', ('0', 'q2')], ['q2', ('1', 'q1')]]

Answer 5

You could get nested dictionaries from your string (a little less straightforward than the previous answers). Thanks to Alex Martelli for his answer to Update value of a nested dictionary of varying depth

import ast

def update(d, u):
    for k, v in u.iteritems():
        if isinstance(v, dict):
            r = update(d.get(k, {}), v)
            d[k] = r
        else:
            d[k] = u[k]
    return d

def listToDict(l):
    temp = l[-1]
    for value in l[-2::-1]:
        temp = {value: temp}
    return temp

input = "[['q1', '0', 'q1'], ['q1', '1', 'q2'], ['q2', '0', 'q2'], ['q2', '1', 'q1']]"

res = {}
for l in ast.literal_eval(input):
    update(res ,listToDict(l))
print res

Output:

{'q1': {'1': 'q2', '0': 'q1'}, 'q2': {'1': 'q1', '0': 'q2'}}