Python serialization – Why pickle?

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Pickling is a way to convert a python object (list, dict, etc.) into a character stream. The idea is that this character stream contains all the information necessary to reconstruct the object in another python script.

As for where the pickled information is stored, usually one would do:

with open('filename', 'wb') as f:
    var = {1 : 'a' , 2 : 'b'}
    pickle.dump(var, f)

That would store the pickled version of our var dict in the ‘filename’ file. Then, in another script, you could load from this file into a variable and the dictionary would be recreated:

with open('filename','rb') as f:
    var = pickle.load(f)

Another use for pickling is if you need to transmit this dictionary over a network (perhaps with sockets or something.) You first need to convert it into a character stream, then you can send it over a socket connection.

Also, there is no “compression” to speak of here…it’s just a way to convert from one representation (in RAM) to another (in “text”).

About.com has a nice introduction of pickling here.

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