Documentation

In the 6th tutorial chapter about Modules, the term "source module" is used.

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.

It isn't really specified what a "source module" is exactly. I think the original python script/module and not the compiled pyc file(s) is meant but I also think this isn't really obvious here (although a hint is given by the phrase "To support a non-source (compiled only)" in the next sentence). My initial suggestion:

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, which refers to the non-compiled python script or 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.