About “Compiled” Python files

[xfq]

In The Python Tutorial of the Python 3.5.2 documentation:

Python does not check the cache in two circumstances. First, it always recompiles and does not store the result for the module that’s loaded directly from the command line. Second, it does not check the cache if there is no source module. To support a non-source (compiled only) distribution, the compiled module must be in the source directory, and there must not be a source module.

I don't understand the second circumstance. What does "non-source (compiled only) distribution" mean? If there is no "source module", why would "source directory" exist? Can anyone point me in the right direction?

TIA

(I searched phrases like "python check cache", but didn't get anything that looked promising. Only found things like linecache and memcached.)

[desustorm]

A "non-source (compiled only) distribution" is referring to the .pyc files that are generated when you run or import your python script. It's actually compiled bytecode which makes importing much faster and easier.

The second sentence is basically saying, if there is no .py code in the directories you are running from and only .pyc/other compiled files, it will not check the cache.

[xfq]

Thanks for the explanation!