Scientific Computing with Python 3

Pickling

The read and write methods you just saw convert data to strings before writing. Complex types (such as objects and classes) cannot be written this way. With Python’s pickle module, you can save any object and also multiple objects to file.

Data can be saved in plaintext (ASCII) format or using a slightly more efficient binary format. There are two main methods: dump, which saves a pickled representation of a Python object to a file, and load, which retrieves a pickled object from the file. The basic usage is like this:

import pickle with open('file.dat','wb') as myfile:     a = random.rand(20,20)     b = 'hello world'     pickle.dump(a,myfile)    # first call: first object     pickle.dump(b,myfile)    # second call: second object import ...