How to find platform-specific directories
Two Python libraries for this task are appdirs and platformdirs, which tell you the location of the platform-specific cache directory and other similar directories.
I was writing a Python library that might need to cache some results. On macOS, that sort of app or library-specific cache should be written to ~/Library/Caches, but that path will be different on other operating systems. I had a vague memory of a library that can knows what path to use on different platforms, and I wanted to write down what it was.
appdirs
appdirs is the library I was remembering. It tells you the directory where you should store data, config, caches and logs.
Here’s an example on my Mac:
>>> from appdirs import *
>>> user_cache_dir(appname="My Great App", appauthor="Alex Chan")
'/Users/alexwlchan/Library/Caches/My Great App'
And the same code on my Debian web server:
>>> from appdirs import *
>>> user_cache_dir(appname="My Great App", appauthor="Alex Chan")
'/home/alexwlchan/.cache/My Great App'
Neat!
It distinguishes between the “user” and the “site” directories – where the latter seems to mean “all uses of the system”. In macOS terms, it’s the difference between ~/Library and /Library.
Although the project is “officially deprecated”, it still seems to work – and it’s delivered as a single file, which means you could copy it into your project without using pip.
platformdirs
platformdirs is the successor to appdirs. It’s actively maintained, and knows about a wider number of directories – for example, a user’s desktop and downloads folder.
Here’s an example on my Mac:
>>> from platformdirs import *
>>> user_downloads_dir()
'/Users/alexwlchan/Downloads'
And my Debian web server:
>>> from platformdirs import *
>>> user_downloads_dir()
'/home/alexwlchan/Downloads'
It also has all the functions provided by appdirs.
Which to choose?
I didn’t implement the caching feature today, so I didn’t end up choosing a library.
I find it slightly annoying that both libraries return str, because I’m trying to move all of my code to use pathlib.Path. I could obviously wrap the results, but I’d rather the library did it for me.
I like the simplicity of appdirs, because I don’t think I need all of the directories offered by platformdirs – but that’s the only one that’s actively maintained.
If I need this sort of functionality in the future, I might look at both of these libraries, then replicate the small amount I need in a file in my project – and convert it to pathlib.Path while I’m there. I could bring in one function rather than an entire library. (And understanding this code would allow me to port it to other languages if necessary.)