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From: "Ivan Evstegneev" <webmailgroups@gmail.com>
To: <python-list@python.org>
Subject: Tuple of lists concatenation  -  function vs comprehension
Date: Sun, 7 Dec 2014 17:07:31 +0200
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Xref: csiph.com comp.lang.python:82058

Hello,

When I have worked  in Python shell (IDLE) I found this issue:

>>>x = ([1, 2], [3, 4], [5, 6])
>>>L = []
>>>for I in x:
	L.extend(i)

>>>L
[1,2,3,4,5,6]

But when I try to make comprehension using above expression, I get this:

>>>x = ([1, 2], [3, 4], [5, 6])
>>>L = []
>>> [L.extend(i) for i in x]
[None, None, None]

But this works fine within function:

>>> def myfunc():
	x = ([1, 2], [3, 4], [5, 6])
	L = []
	[L.extend(i) for i in x]
	print(L)

>>>myfunc()
[1, 2, 3, 4, 5, 6]

The question is why I'm getting empty list while working with comprehension
in interactive console? 

Thanks for your help.

Ivan.