[Tutor] how to compare elements of 2 lists

[Chris Fuller]

On Wednesday 26 December 2007 10:03, Alan Gauld wrote:
> I thought I was following this but now I'm not sure.
>
> Do you mean that if I have a list L that contains an arbitrary
>
> number of sublists that I can call zip using:
> >>> zip(*L)
>
> rather than
>
> >>> zip(L[0],L[1],...., L[n])
>
> If so I agree.
>
Yes.  You could build up a string and call eval(), but otherwise this wouldn't 
be possible, without iterating through manually.  (using evail() is usually 
not a good idea, avoid it if you can)

> But any time that you use the *[] format it is easier to
> just put the content of the [] into the zip directly, which is what,
> I think, Kent is saying?
>

Yes, for the original example, zip(a,b) is equivalent, and probably clearer.  
Certainly simpler.  Sorry to be confusing.  I realize now that lots of my 
code have lists of known length and need a little tweaking :)

I just remembered another way to do this, with map():
>>> a=range(4)
>>> b=['a','b','c','d']
>>> map(None,a,b)
[(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')]

This also doesn't complain if the lists are uneven, but instead of truncating, 
it pads the short ones with None's.  I almost never use map() now that we 
have list comprehensions, however.  map(None, *(a,b)) also works if you 
are "transposing" an unknown number of lists.

Cheers