Global variable not working from module function in ipython

Question

I'm sure someone's already answered this, but I can't find it.

I have a script test.py who's sole purpose of existence is to place the variable var into the global namespace:

def test():
    global var
    var = 'stuff'

Here's what happens when I run test.py in ipython using %run, then run test(), and then try to access var.

Python 3.6.4 |Anaconda, Inc.| (default, Jan 16 2018, 10:22:32) [MSC v.1900 64 bit (AMD64)]
Type 'copyright', 'credits' or 'license' for more information
IPython 6.2.1 -- An enhanced Interactive Python. Type '?' for help.

In [1]: %run test.py

In [2]: test()

In [3]: var
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-3-84ddba356ca3> in <module>()
----> 1 var

NameError: name 'var' is not defined

In [4]:

Any idea what's happening? Or how to generally bring it into the local namespace?

Possible duplicate of Is it possible to define global variables in a function in Python — Bruno Henrique
– Bruno Henrique, Commented May 1, 2018 at 20:02
The question technically is a duplicate, but I was still running into the issue. Turns out the issue was not in the global variable part, but in the way I was using IPython. I've updated the question and title to reflect the actual issue present. — James Wright
– James Wright, Commented May 2, 2018 at 12:19

Eugene Yarmash · Accepted Answer · 2018-05-01 21:05:58Z

5

The %run command creates a separate namespace for global variables in the file. It also updates the IPython interactive namespace with all variables defined in the file after execution. So you can either call the function in your script so that the global variable gets created before the file finishes executing:

def test():
    global var
    var = 'stuff'
test()

or use %run -i:

-i run the file in IPython’s namespace instead of an empty one. This is useful if you are experimenting with code written in a text editor which depends on variables defined interactively.

edited May 1, 2018 at 21:05

answered May 1, 2018 at 20:13

Eugene Yarmash

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Comments

Auzy · Accepted Answer · 2018-05-01 20:13:01Z

2

Use %run -i test.py this will run it in the interactive namespace and let you access the global variables.

In [1]: %run -i test.py

In [2]: test()

In [3]: var
Out[3]: 'stuff'

answered May 1, 2018 at 20:13

Auzy

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