Storing Python dictionaries

Question

I'm used to bringing data in and out of Python using CSV files, but there are obvious challenges to this. Are there simple ways to store a dictionary (or sets of dictionaries) in a JSON or pickle file?

For example:

data = {} data ['key1'] = "keyinfo" data ['key2'] = "keyinfo2" 

I would like to know both how to save this, and then how to load it back in.

Answer 1

Pickle save:

try:     import cPickle as pickle except ImportError:  # Python 3.x     import pickle  with open('data.p', 'wb') as fp:     pickle.dump(data, fp, protocol=pickle.HIGHEST_PROTOCOL) 

See the pickle module documentation for additional information regarding the protocol argument.

Pickle load:

with open('data.p', 'rb') as fp:     data = pickle.load(fp) 

---

JSON save:

import json  with open('data.json', 'w') as fp:     json.dump(data, fp) 

Supply extra arguments, like sort_keys or indent, to get a pretty result. The argument sort_keys will sort the keys alphabetically and indent will indent your data structure with indent=N spaces.

json.dump(data, fp, sort_keys=True, indent=4) 

JSON load:

with open('data.json', 'r') as fp:     data = json.load(fp) 

Answer 2

Minimal example, writing directly to a file:

import json json.dump(data, open(filename, 'wb')) data = json.load(open(filename)) 

or safely opening / closing:

import json with open(filename, 'wb') as outfile:     json.dump(data, outfile) with open(filename) as infile:     data = json.load(infile) 

If you want to save it in a string instead of a file:

import json json_str = json.dumps(data) data = json.loads(json_str)