the problem

What directory should your app use for storing user data? If running on Mac OS X, you
should use::

~/Library/Application Support/<AppName>

If on Windows (at least English Win XP) that should be::

C:\Documents and Settings\<User>\Application Data\Local Settings\<AppAuthor>\<AppName>

or possibly::

C:\Documents and Settings\<User>\Application Data\<AppAuthor>\<AppName>

for roaming profiles <http://bit.ly/9yl3b6>_ but that is another story.

On Linux (and other Unices) the dir, according to the XDG spec <http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html>_
(and subject to some interpretation), is::

~/.config/<appname>     # note AppName was lowercased

appdirs to the rescue

This kind of thing is what the appdirs module is for. appdirs will
help you choose an appropriate:

• user data dir (user_data_dir)
• user cache dir (user_cache_dir)
• site data dir (site_data_dir)
• user log dir (user_log_dir)

and also:

• is a single module so other Python packages can include their own private copy
• is slightly opinionated on the directory names used. Look for "OPINION" in
  documentation and code for when an opinion is being applied.

some example output

On Mac OS X::

>>> from appdirs import *
>>> appname = "SuperApp"
>>> appauthor = "Acme"
>>> user_data_dir(appname, appauthor)
'/Users/trentm/Library/Application Support/SuperApp'
>>> site_data_dir(appname, appauthor)
'/Library/Application Support/SuperApp'
>>> user_cache_dir(appname, appauthor)
'/Users/trentm/Library/Caches/SuperApp'
>>> user_log_dir(appname, appauthor)
'/Users/trentm/Library/Logs/SuperApp'

On Windows 7::

>>> from appdirs import *
>>> appname = "SuperApp"
>>> appauthor = "Acme"
>>> user_data_dir(appname, appauthor)
'C:\\Users\\trentm\\AppData\\Local\\Acme\\SuperApp'
>>> user_data_dir(appname, appauthor, roaming=True)
'C:\\Users\\trentm\\AppData\\Roaming\\Acme\\SuperApp'
>>> user_cache_dir(appname, appauthor)
'C:\\Users\\trentm\\AppData\\Local\\Acme\\SuperApp\\Cache'
>>> user_log_dir(appname, appauthor)
'C:\\Users\\trentm\\AppData\\Local\\Acme\\SuperApp\\Logs'

On Linux::

>>> from appdirs import *
>>> appname = "SuperApp"
>>> appauthor = "Acme"
>>> user_data_dir(appname, appauthor)
'/home/trentm/.config/superapp
>>> site_data_dir(appname, appauthor)
'/etc/xdg/superapp'
>>> user_cache_dir(appname, appauthor)
'/home/trentm/.cache/superapp'
>>> user_log_dir(appname, appauthor)
'/home/trentm/.cache/superapp/log'

AppDirs for convenience

::

>>> from appdirs import AppDirs
>>> dirs = AppDirs("SuperApp", "Acme")
>>> dirs.user_data_dir
'/Users/trentm/Library/Application Support/SuperApp'
>>> dirs.site_data_dir
'/Library/Application Support/SuperApp'
>>> dirs.user_cache_dir
'/Users/trentm/Library/Caches/SuperApp'
>>> dirs.user_log_dir
'/Users/trentm/Library/Logs/SuperApp'

Per-version isolation

If you have multiple versions of your app in use that you want to be
able to run side-by-side, then you may want version-isolation for these
dirs::

>>> from appdirs import AppDirs
>>> dirs = AppDirs("SuperApp", "Acme", version="1.0")
>>> dirs.user_data_dir
'/Users/trentm/Library/Application Support/SuperApp/1.0'
>>> dirs.site_data_dir
'/Library/Application Support/SuperApp/1.0'
>>> dirs.user_cache_dir
'/Users/trentm/Library/Caches/SuperApp/1.0'
>>> dirs.user_log_dir
'/Users/trentm/Library/Logs/SuperApp/1.0'