CACHEDIR.TAG for Python

This library handles CACHEDIR.TAG files. Allowing any arbitrary directory to be marked as a cache directory.

A CACHEDIR.TAG file indicates a directory that contain cached data, e.g.

• downloads
• previews, and thumbnails
• build artefacts, and other intermediate results

Cached data is useful, but not essential - if necessary it can be regenerated, or downloaded again. However backup programs, disk cleanup utilities, & other software can't know if an arbitrary path is cached data, unless it is marked.

A directory (and all directories within it) can be marked as a cache by writing a regular file named CACHEDIR.TAG, with the first 43 bytes being

Signature: 8a477f597d28d172789f06886806bc55

After this signature any other text can be included. The specification suggests lines of text beginning with #, encoded as UTF-8. E.g.

# This file is a cache directory tag created by (application name).
# For information about cache directory tags, see:
#	http://www.brynosaurus.com/cachedir/

This library follows that suggestion.

Installation

$ python -m pip install cachedir-tag

Usage

Create your cache directory, if necessary

>>> import os, cachedir_tag
>>> os.mkdir('/var/cache/yourapp')

Tag it, this creates a new CACHEDIR.TAG file

>>> cachedir_tag.tag('/var/cache/yourapp')

Check whether the directory is tagged

>>> cachedir_tag.is_tagged('/var/cache/yourapp')
True

Check whether a sub-directory (which may not exist yet) is tagged

>>> cachedir_tag.is_tagged('/var/cache/yourapp/somedir')
True

Alternatives

Operating systems and similar platforms usually have conventions about where to place cached data. A CACHEDIR.TAG file isn't needed if you follow these conventions, but it doesn't hurt either.

More information

• Cache Directory Tagging Specification by Bryan Ford