Python – Storing Python dictionaries

dictionaryjsonpicklepythonsave

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.

Best Solution

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)