How execute at least two python files at once when imported?

[David Raymond]

"Why is importing modules in parallel bad?"

In general I'd say that
"import foo"
is supposed to be there because you want the classes, functions, variables etc. in foo to be available in your current program. A module should never run a whole bunch of time consuming stuff when it's imported.

If you want to "run foo" rather than import it, then inside foo all the "running" code should be in a function which can be called later. If you want foo to be runnable directly you can then call that function from the classic if __name__ == "__main__": construct. That lets foo be importable, and lets you pick when you want the actual long stuff to run.

#In foo.py
<various class, function definitions, etc>
def run_long_task():
    long_stuff_here
if __name__ == "__main__":
    #foo.py is being called directly, not imported
    run_long_task()


So your main program should look something like:

import foo  #quick as just the definitions are processed
foo.run_long_task()

Or to "run" multiple other things at once it should look more like:

import threading  #multiprocessing, or other module here
import foo  #quick as just the definitions are processed
import bar  #quick as just the definitions are processed

kick off foo.run_long_task() as its own thread/process/task/etc
kick off bar.run_long_task() as its own thread/process/task/etc

wait for them to finish and process results, or do stuff while they're running


So again, "import" should never be used to "run" another file, just to "bring in the stuff from" another file. And any file designed to be imported should not run extra stuff during that import.