Question

I have the following code:

>>> word_array = defaultdict(list)
>>> word_array['first'].append(1)
>>> word_array['first'].append(2)
>>> word_array
defaultdict(<type 'list'>, {'first': [1, 2]})

I converted it to string the whole data structure, but when i try to convert it from string i can’t, i get the following:

>>> ast.literal_eval(str(word_array))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/ast.py", line 49, in literal_eval
    node_or_string = parse(node_or_string, mode='eval')
  File "/usr/lib/python2.7/ast.py", line 37, in parse
    return compile(source, filename, mode, PyCF_ONLY_AST)
  File "<unknown>", line 1
    defaultdict(<type 'list'>, {'first': [1, 2]})
                ^
SyntaxError: invalid syntax

Is there any better solution to this.

Answer 1

All you want to do here is serialize your data structure into a string, and then deserialize it back into a data structure. Don’t use things like ast.literal_eval in production. Just use pickle:

import pickle
from collections import defaultdict

word_array = defaultdict(list)
word_array['first'].append(1)
word_array['first'].append(2)

s = pickle.dumps(word_array)
other = pickle.loads(s)

print other

Gives:

defaultdict(<type 'list'>, {'first': [1, 2]})