how can I access a global variable from another .py file in python?

Question

I created two files, and when I run a.py, result is {'1': '1'}, it's correct. however, running b.py, the result is none. How can I get the value of requests from b.py?

a.py:

requests = {}

def set_value():
   global requests
   requests["1"] = "1"

if __name__ == "__main__":  
    set_value()
    print(requests)

b.py:

import a

def get_value():
   print(a.requests)


if __name__ == "__main__":
   get_value()

__name__ == "__main__" is false if the file containing it was imported from another file. — Michael Butscher
– Michael Butscher, Commented Jun 3, 2019 at 2:19
You need to call set_vale to get 1:1 added to requests. Importing a doesn't do this. So from b, you can call a.set_vale() before calling get_value. — Tom Karzes
– Tom Karzes, Commented Jun 3, 2019 at 2:19
It is returning null because set_vale() is not called whenever get_value() is called in b.py. Try calling set_vale() in get_value() of b.py. — Harshil Shah
– Harshil Shah, Commented Jun 3, 2019 at 2:20

Lord Elrond · Accepted Answer · 2019-06-03 02:22:42Z

1

if __name__ == "__main__": means that the code following it will only be executed when the file is called explicitly with python3 filename.py from the command line. Since you are simply importing your file and not executing it, the global variable is never set.

Also, python variables are all "global" variables when declared outside of a function, and the global keyword is only needed when you want to declare a global variable inside of a function.

To fix this, change a.py to the following:

requests = {}

def set_vale():
    requests["1"] = "1"

set_vale()

answered Jun 3, 2019 at 2:22

Lord Elrond

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