__main__ 中的多处理和池 - 如何在 __main__ 之外获取 output？

Question

Based on this answer ( https://stackoverflow.com/a/20192251/9024698 ), I have to do this:

from multiprocessing import Pool

def process_image(name):
    sci=fits.open('{}.fits'.format(name))
    <process>

if __name__ == '__main__':
    pool = Pool()                         # Create a multiprocessing Pool
    pool.map(process_image, data_inputs)  # process data_inputs iterable with pool

to multi-process a for loop.

However, I am wondering, how can I get the output of this and further process if I want?

It must be like that:

if __name__ == '__main__':
    pool = Pool()                         # Create a multiprocessing Pool
    output = pool.map(process_image, data_inputs)  # process data_inputs iterable with pool
    # further processing

But then this means that I have to put all the rest of my code in __main__ unless I write everything in functions which are called by __main__ ?

The notion of __main__ has been always pretty confusing to me.

Answer 1

if __name__ == '__main__': is literally just "if this file is being run as a script, as opposed to being imported as a module, then do this". __name__ is a hidden variable that gets set to '__main__' if it's being run as a script. why it works this way is beyond the scope of this discussion but suffice it to say it has to do with how python evaluates sourcefiles top-to-bottom.

In other words, you can put the other two lines anywhere you want - in a function, probably, that you call elsewhere in the program. You could return output from that function, or do other processing on it, or etc., whatever you happen to need.