Files with bytecode are really created only for imported modules?

Question

In my system I have created a Python application that is composed by more than one file. The directory structure of the application is the following:

application_directory
  |- file_a.py
  |- file_b.py
  |- file_c.py

Inside the script file_c.py are present the following imports:

import file_a
from file_b import ClassB

When I execute the script file_c.py by the command:

> python3 file_c.py

in the folder application_folder is created a directory called __pycache__ and inside it two files with bytecode (see this link to get more information about the concept of compilation in Python) and called:

__pycache__/file_a.cpython-310.pyc
__pycache__/file_b.cpython-310.pyc

To understand why are created this files I have search a lot and I have found many links about this topic. The most clear could be this answer that seems perfect to understand what happens in my context.

In the answer is present the following sentence:

Running a script is not considered an import and no .pyc will be created.

So I am asking: only for modules imported are created a file with bytecode? Why is there this difference in the management of imported modules respect to not imported scripts?

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EDIT I have found this other answer very useful to better understand how works CPython, the concept of bytecode and the file .pyc saved to the hard disk.

Answer 1

All files are compiled before being executed, python just does not write them to a file. In this case, because they're imports, modules are compiled and then cached, to make subsequent runs faster.