How do you convert a stringed dictionary to a Python dictionary?

Question

I have the following string which is a Python dictionary stringified:

some_string = '{123: False, 456: True, 789: False}'

How do I get the Python dictionary out of the above string?

Answer 1

Well, you can do

d = eval(some_string)

But if the string contains user input, it's a bad idea because some random malicious function could be in the expression. See http://stackoverflow.com/questions/1112665/safety-of-python-eval-for-list-deserialization

So a safer alternative might be:

import ast
d = ast.literal_eval(some_string)

From http://docs.python.org/library/ast.html#ast.literal_eval :

The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dicts, booleans, and None.

Answer 2

Use ast.literal_eval:

Safely evaluate an expression node or a string containing a Python expression. The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dicts, booleans, and None.

This can be used for safely evaluating strings containing Python expressions from untrusted sources without the need to parse the values oneself.

Example:

>>> some_string = '{123: False, 456: True, 789: False}'
>>> import ast
>>> ast.literal_eval(some_string)
{456: True, 123: False, 789: False}

Answer 3

The only safe way to do it is with ast.literal_eval (it's safe because, differently from built-in eval, """The string or node provided may only consist of the following Python literal structures: strings, numbers, tuples, lists, dicts, booleans, and None.""".