I have been trying to convert a string of dictionary objects as given below

"{'Cmd': None, 'Hostname': None, 'Entrypoint': None, 'Env': None,     'OpenStdin': False, 
'Tty': False, 'Domainname': None, 'Image': u'nginx:latest', 'HostConfig':   
{'Binds': None, 'RestartPolicy': {}, 'NetworkMode': u'bridge', 'Dns': None, 
'Links': [], 'PortBindings': {}, 'DnsSearch': None, 'Privileged': False,
'VolumesFrom': []}, 'ExposedPorts': {}, 'User': None}"

to python dictionary.

But the solutions came up while searching were suggesting to use python ast library for the purpose. as

import ast

And it works fine. But is ast library is built indented to solve problems like this ? Is there any good approach other than this to solve the problem ?

  • \$\begingroup\$ Welcome to Code Review! I'm afraid this question does not match what this site is about. Code Review is about improving existing, working code. The example code that you have posted is not reviewable in this form because it's so short it leaves us guessing at your intentions. Unlike Stack Overflow, Code Review needs to look at concrete code in a real context. Please see Why is hypothetical example code off-topic for CR? In particular though, we'd need to know where the data comes from to understand what to expect from it. \$\endgroup\$ Oct 6, 2015 at 10:05
  • \$\begingroup\$ Usually when you try to do something with an eval, there's a better way available. \$\endgroup\$
    – Mast
    Oct 6, 2015 at 10:15
  • 2
    \$\begingroup\$ Hmm... While your code is short, it looks real to me, and I see no reason to close it. To me your code needs no guessing..... \$\endgroup\$
    – rolfl
    Oct 6, 2015 at 10:33
  • 3
    \$\begingroup\$ You tagged the question as json, but your string is not quite valid JSON (None instead of null, etc.) -- if it were, you could simply use json.loads from the Python standard library. \$\endgroup\$ Oct 6, 2015 at 14:14
  • \$\begingroup\$ And don't cross-post. \$\endgroup\$
    – jonrsharpe
    Oct 6, 2015 at 14:32

2 Answers 2


To answer your question, yes ast is ok to be used for this. Per the documentation for literal_eval:

Safely evaluate an expression node or a Unicode or Latin-1 encoded string containing a Python literal or container display. 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 values from untrusted sources without the need to parse the values oneself. It is not capable of evaluating arbitrarily complex expressions, for example involving operators or indexing.


Yes. Whenever you are choosing libraries, make sure that the libraries are not only comfortable with IPython consoles like Jupyter, but also habituated to the Python shell.

Hence it is easier to use YAML:

import yaml

s= #your string supposed to be

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