[] and NoneType
Chris Gonnerman
chris.gonnerman at newcenturycomputers.net
Tue Aug 20 21:57:25 EDT 2002
----- Original Message -----
From: "beilin" <bzhang at sangamo.com>
> Hi,
>
> Could anyone explain to me why [].append("test") returns None? What is
> the difference between the following two?
> >>> a = []
> >>> a.append("test")
> >>> print a
> ['test']
> >>>
>
> and
>
> >>> a = [].append("test")
> >>> print a
> None
> >>>
>
> I am confused. Thanks
Sure. You are thinking in Functional Programming terms;
Python has only partial support for that. In particular,
the .append method for lists does NOT return the list.
Ever. It returns None.
Sorry.
This is a subject of frequent discussion around here, but
in the final analysis, that's how it is.
The first form you show is correct, the second incorrect.
Chris Gonnerman -- chris.gonnerman at newcenturycomputers.net
http://newcenturycomputers.net
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