Storing Python dictionaries

Question

Are there simple ways to store a dictionary (or multiple dictionaries) in, for example, a JSON or pickle file?

For example, if I have some data like:

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

How can I save it in a file, and then later load it back in to the program from the file?

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_{JSON and Pickle can also be used to store more complex structured data. This question may also include answers that are specific to the case of a simple dictionary like the one described. For more general approaches, see How can I write structured data to a file and then read it back into the same structure later?. Note that the technique of converting the data to storable data is called serialization, and re-creating the data structure is called deserialization; storing the data for later use is called persistence.}

_{See also What do files actually contain, and how are they "read"? What is a "format" and why should I worry about them? for some theory about how files work, and why structured data cannot just be written into and read from files directly.}

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)

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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)