are global variables visible to subprocess and changable by subprocess?

Question

A quick question for Python 2.7

Are global variables visible to a subprocess?

Can a subprocess change the values of global variables?

Many thanks.

if you want to run closely related Python code in child processes then consider [`multiprocessing` module](http://docs.python.org/3/library/multiprocessing.html): it allows to send objects between processes just by passing them as function parameters (among other IPC methods) — jfs, Mar 27 '14 at 17:51

score 3 · Answer 1 · answered Mar 27 '14 at 14:21

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No, global variables are not visible to a sub-process. Variables are private to each process. If you want to share variables then you need to use some form of inter-process communication.

answered Mar 27 '14 at 14:21

David Heffernan

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Can you share an example of inter-process communication? – Shirley Mar 27 '14 at 14:26
You can find oodles of info here: http://www.google.com/webhp?q=python%20ipc#q=python+ipc – David Heffernan Mar 27 '14 at 14:39

score 2 · Accepted Answer · answered Mar 27 '14 at 14:25

2

The processes doesn't share the variables in a general operating system terms. Use some communication mechanism like message passing, shared memory etc to achieve the inter process communication.

answered Mar 27 '14 at 14:25

Ankit Kumar

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Can you share an example of inter-process communication? – Shirley Mar 27 '14 at 14:27
you can refer to this discussion for this [http://stackoverflow.com/questions/6920858/interprocess-communication-in-python](http://stackoverflow.com/questions/6920858/interprocess-communication-in-python) – Ankit Kumar Mar 27 '14 at 14:31

score 0 · Answer 3 · answered Apr 04 '14 at 09:32

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Maybe the simplest way is write those into a file and read from the file in another process, although this might take extra time.

answered Apr 04 '14 at 09:32

Shirley

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are global variables visible to subprocess and changable by subprocess?

3 Answers3