Saullo Castro Saullo Castro - 1 year ago 176
Python Question

Python, cPickle, pickling lambda functions

I have to pickle an array of objects like this:

import cPickle as pickle
from numpy import sin, cos, array
tmp = lambda x: sin(x)+cos(x)
test = array([[tmp,tmp],[tmp,tmp]],dtype=object)
pickle.dump( test, open('test.lambda','w') )

and it gives the following error:

TypeError: can't pickle function objects

Is there a way around that?

Answer Source

The built-in pickle module is unable to serialize several kinds of python objects (including lambda functions, nested functions, and functions defined at the command line).

The picloud package includes a more robust pickler, that can pickle lambda functions.

from pickle import dumps
f = lambda x: x * 5
dumps(f) # error
from cloud.serialization.cloudpickle import dumps
dumps(f) # works

PiCloud-serialized objects can be de-serialized using the normal pickle/cPickle load and loads functions.

Dill also provides similar functionality

>>> import dill           
>>> f = lambda x: x * 5
>>> dill.dumps(f)
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