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From: Wolfgang Maier <wolfgang.maier@biologie.uni-freiburg.de>
Subject: Re: unsupported operand type(s) python v2.7
Date: Tue, 20 Oct 2015 11:00:08 +0200
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Xref: csiph.com comp.lang.python:97830

On 20.10.2015 10:44, ngangsia akumbo wrote:
>>>> def n():
> 	34 * 2
>
> 	
>>>> def g():
> 	4 + 2
>

Your n and g functions do not have an explicit return so, after doing 
their calculations and throwing the result away, they return None.

>>>> def ng():
> 	return n() + g()
>
>>>> ng()
>
> Traceback (most recent call last):
>    File "<pyshell#14>", line 1, in <module>
>      ng()
>    File "<pyshell#13>", line 2, in ng
>      return n() + g()
> TypeError: unsupported operand type(s) for +: 'NoneType' and 'NoneType'
>

The attempt in ng to add None to None then produce the exception you are 
seeing.