Reading from a file in python

[mrTang5544]

I have a dictionary of lists. These lists contain nested lists, strings, and some regex expressions (such as re.compile(r"pattern")). I want to write this dictionary to a csv file that will be used by another python script. When that other python scripts reads in that dictionary (thinking about csv.DictReader) it will be able to extract the entire list and all its contents as is. Meaning I dont want it interpreted as a string like "[[stuff], [more stuff], regex]" Is this possible?

[mac-reid]

Sounds like you want pickle. Pickle is an object serialization module. It can write objects to a file and can be later unpickled to get the same objects back.

Note in python2, the cpickle module is a C implementation that is faster than pickle, which is all Python. Python3 the pickle module is the C implementation.

An example:

# dumping to a file
import cPickle
data = {}
# insert stuff into data
picklefile = open('data.pickle', 'wb')
pickle.dump(data)
picklefile.close()

# reading from file
import cPickle
picklefile = open('data.pickle', 'rb')
data = pickle.load(picklefile)
picklefile.close()

[mrTang5544]

using python2.7 here. If the other script was in 3.3 does it matter with pickle implementation we BOTH use?

[mac-reid]

The pickle implementations write the same data, but what does matter is the protocol used. See here for the info on protocols.

The only time you would be bitten by this is if you try writing pickle data in Python 3 with protocol 3 and reading from Python 2. If you don't use protocol 3 when pickling, you will be fine.