Saving a Python dict to a file using pickle

Per Programming Python, 3rd Edition, there are a number of methods to store persistent data with Python:

• I often use flat files to read or write text (string) data using the os library.
• Flat files are read sequentially, but dbm files allow for keyed access to string data
• The pickle module can be used to store non-string Python data structures, such as Python dicts. However, the data is not keyed as with dbm files.
• shelve files combine the best of the dbm and pickle methods by storing pickled objects in dbm keyed files.
• I've read good things about the ZODB object-oriented database, but I don't know too much about it. Per the book, it is a more powerful alternative to shelves.
• The final option is interfacing with a full-fledged SQL relational databases. As I mentioned before, Python 2.5 has an interface to SQLite as part of the standard distribution.

Here is an example using pickle which writes a Python dict to a file and reads it back again:

import pickle# write python dict to a filemydict = {'a': 1, 'b': 2, 'c': 3}output = open('myfile.pkl', 'wb')pickle.dump(mydict, output)output.close()# read python dict back from the filepkl_file = open('myfile.pkl', 'rb')mydict2 = pickle.load(pkl_file)pkl_file.close()print mydictprint mydict2

Results:

{'a': 1, 'c': 3, 'b': 2}{'a': 1, 'c': 3, 'b': 2}