Pickling and unpickling in python

[Humble]

pickling and unpickling is a very useful feature in python which is used for serialization and de-serialization. Sometime its necessary to convert an object strucutre to a byte stream and get it back to the original state once its done . This is achieved with the help of pickling and unpickling .

Pickling” is the process whereby a Python object hierarchy is converted into a byte stream, and “unpickling” is the inverse operation, whereby a byte stream is converted back into an object hierarchy.

For ex:

>>>> import pickle
>>> pickle.__doc__
'Create portable serialized representations of Python objects.\n\nSee module cPickle for a (much) faster implementation.\nSee module copy_reg for a mechanism for registering custom picklers.\nSee module pickletools source for extensive comments.\n\nClasses:\n\n    Pickler\n    Unpickler\n\nFunctions:\n\n    dump(object, file)\n    dumps(object) -> string\n    load(file) -> object\n    loads(string) -> object\n\nMisc variables:\n\n    __version__\n    format_version\n    compatible_formats\n\n'

>>> with open('/tmp/hum', 'w') as f:
...     tran_dict = {1 : 'monday' , 2 : 'tuesday', 3:'wednesday'}
...     pickle.dump(tran_dict, f)
...
>>>



Once its 'pickled' , if you cross-check the file you can see:

>@humbles-lap ~]$ cat /tmp/hum
(dp0
I1
S'monday'
p1
sI2
S'tuesday'
p2
sI3
S'wednesday'
p3
s.
[@humbles-lap ~]$


Now to unpickle or to get it back , you can try something like below::

>>>> fDes = open('/tmp/hum','r')
>>> pickle.load(fDes)
{1: 'monday', 2: 'tuesday', 3: 'wednesday'}




One of the use case for using pickle is , if you want to transfer dictionary object  over network ... There are other options to do that , for ex: json.. how-ever sometime this may be handy...

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