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

Is there any way to parse string so that the dictionary key is the first element of the list and the value of the key is the next to elements. For example:

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

you can't have duplicate elements in dictionary as keys. q1 and q2 are repeated twice in your expected output, you can't have this. — venpa, Dec 04 '14 at 08:25
unless you change the behaviour of a Python dictionnary by redefining a class but I guess that's not the purpose :) — Colonel Beauvel, Dec 04 '14 at 08:28
is there a way to add another value to an existing key in a dictionary? — user3246978, Dec 04 '14 at 08:29
yes, you could have like:`{'q1': [('0','q1'), ('1','q2')], 'q2': [('0','q2'), ('1', 'q1')]}`. is this you want? — venpa, Dec 04 '14 at 08:40

score 4 · Accepted Answer · answered Dec 04 '14 at 08:31

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')]]

this worked and my problem as been fixed. Thank you! – user3246978 Dec 04 '14 at 09:20 — user3246978, Dec 04 '14 at 09:20

score 3 · Answer 2 · answered Dec 04 '14 at 08:29

3

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']}

answered Dec 04 '14 at 08:29

AlvaroAV

10,335
12
60
91

1

A list of lists is a valid JSON, the issue is OP's string contains single quotes instead of double quotes. – Ashwini Chaudhary Dec 04 '14 at 08:45

Aristide · Answer 3 · 2014-12-04T09:14:43.303

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 :-)

Avinash Garg · Answer 4 · 2014-12-04T08:56:00.567

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

edited Dec 04 '14 at 08:56

answered Dec 04 '14 at 08:34

Avinash Garg

1,374
14
18

1

This is not what OP asked for – Hackaholic Dec 04 '14 at 08:37
@Hackaholic yes i kno just giving idea – Avinash Garg Dec 04 '14 at 08:39
I didnt downvote . but as i said OP dosent want this – Hackaholic Dec 04 '14 at 08:58

score 2 · Answer 5 · edited May 23 '17 at 11:43

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'}}

how to parse a string into a dictionary

5 Answers5

Linked

Related