Data Serialization

Syntax#

• unpickled_string = pickle.loads(string)
• unpickled_string = pickle.load(file_object)
• pickled_string = pickle.dumps([(”, ‘cmplx’), {(‘object’,): None}], pickle.HIGHEST_PROTOCOL)
• pickle.dump((”, ‘cmplx’), {(‘object’,): None}], file_object, pickle.HIGHEST_PROTOCOL)
• unjsoned_string = json.loads(string)
• unjsoned_string = json.load(file_object)
• jsoned_string = json.dumps((‘a’, ‘b’, ‘c’, [1, 2, 3]))
• json.dump((‘a’, ‘b’, ‘c’, [1, 2, 3]), file_object)

Parameters#

• Cross language support
• Human readable
• Unlike pickle, it doesn’t have the danger of running arbitrary code

Why not using JSON?

• Doesn’t support Pythonic data types
• Keys in dictionaries must not be other than string data types.

Why Pickle?

• Great way for serializing Pythonic (tuples, functions, classes)
• Keys in dictionaries can be of any data type.

Why not Pickle?

• Cross language support is missing
• It is not safe for loading arbitrary data

Serialization using JSON

JSON is a cross language, widely used method to serialize data

Supported data types : int, float, boolean, string, list and dict. See -> JSON Wiki for more

Here is an example demonstrating the basic usage of JSON :-

import json

families = (['John'], ['Mark', 'David', {'name': 'Avraham'}])

# Dumping it into string
json_families = json.dumps(families)
# [["John"], ["Mark", "David", {"name": "Avraham"}]]

# Dumping it to file
with open('families.json', 'w') as json_file:
    json.dump(families, json_file)

# Loading it from string
json_families = json.loads(json_families)

# Loading it from file
with open('families.json', 'r') as json_file:
    json_families = json.load(json_file)

See JSON-Module for detailed information about JSON.

Serialization using Pickle

Here is an example demonstrating the basic usage of pickle:-

# Importing pickle
try:
    import cPickle as pickle  # Python 2
except ImportError:
    import pickle  # Python 3

# Creating Pythonic object:
class Family(object):
    def __init__(self, names):
        self.sons = names

    def __str__(self):
        return ' '.join(self.sons)

my_family = Family(['John', 'David'])

# Dumping to string
pickle_data = pickle.dumps(my_family, pickle.HIGHEST_PROTOCOL)

# Dumping to file
with open('family.p', 'w') as pickle_file:
    pickle.dump(families, pickle_file, pickle.HIGHEST_PROTOCOL)

# Loading from string
my_family = pickle.loads(pickle_data)

# Loading from file
with open('family.p', 'r') as pickle_file:
    my_family = pickle.load(pickle_file)

See Pickle for detailed information about Pickle.

WARNING: The official documentation for pickle makes it clear that there are no security guarantees. Don’t load any data you don’t trust its origin.