Difference in formatting list and tuple values
Sean 'Shaleh' Perry
shalehperry at attbi.com
Thu Dec 13 18:08:07 CET 2001
On 13-Dec-2001 Sue Giller wrote:
> I am trying to format values from either a list or a tuple, and I am
> getting the following odd (to me) behavior. I can format the tuple
> entry using %d, but I get an error when I use the same formatting
> for the same data in a list.
> Why does this happen?
>>>> l = [1,2,3] # list
>>>> t = (1,2,3) # tuple
>>>> print "%02d" % t[:1] # format first entry in tuple ok
>>>> print "%02d" % l[:1] # get error with list
> Traceback (most recent call last):
> File "<interactive input>", line 1, in ?
> TypeError: an integer is required
>>>> print "%02d" % tuple(t[:1]) # cast to a tuple works ok
l[:1] returns , not 1. The ':' is for slicing. It returns a new list (or
tuple, or string) in the range specified. If you just want the first item ask
Casting to a tuple works because the call then becomes:
"%02d" % (1,)
which is what the % operator expects -- a tuple of one item.
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