Python Shelve Module - Python Cheatsheet

Python Shelve Module

From the Python 3 documentation A “shelf” is a persistent, dictionary-like object. The difference with “dbm” databases is that the values (not the keys!) in a shelf can be essentially arbitrary Python objects — anything that the pickle module can handle. This includes most class instances, recursive data types, and objects containing lots of shared sub-objects. The keys are ordinary strings.

Save variables

>>> import shelve

>>> wife = ['Pretty', 'Lovely', 'Nice']
>>> with shelve.open('mydata') as shelf_file:
...     shelf_file['wife'] = wife

Open and read variables

>>> with shelve.open('mydata') as shelf_file:
...     print(type(shelf_file))
...     print(shelf_file['wife'])
...
# <class 'shelve.DbfilenameShelf'>
# ['Pretty', 'Lovely', 'Nice']

Just like dictionaries, shelf values have keys() and values() methods that will return list-like values of the keys and values in the shelf. Since these methods return list-like values instead of true lists, you should pass them to the list() function to get them in list form.

>>> with shelve.open('mydata') as shelf_file:
...     print(list(shelf_file.keys()))
...     print(list(shelf_file.values()))
...
# ['wife']
# [['Pretty', 'Lovely', 'Nice']]