List mutation method gotcha - How well known?

[Bruno Desthuilliers]

Hendrik van Rooyen a écrit :
> Hi,
> 
> I am surprised that it took me so long to bloody my nose on this one.
> 
> It must be well known - and I would like to find out how well known.
> 
> So here is a CLOSED BOOK multiple choice question - no RTFM, 
> no playing at the interactive prompt:
> 
> Given the following three lines of code at the interactive prompt:
> 
> foo = [1,2,3,4]
> x = foo.append(5)
> print x
> 
> What will be the output (choose one):
> 
> 1)  [1,2,3,4]
> 2)  [1,2,3,4,5]
> 3)  That famous picture of Albert Einstein sticking out his tongue
> 4)  Nothing - no output
> 5)  None of the above

answer 5 - list.append returns None, which when printed gives 'None'.

You'll get the same thing with list.sort, list.extend, list.reverse etc...