Loop in a loop?

[Duncan Booth]

Chris <cwitts at gmail.com> wrote:

> You could always pre-pad the lists you are using before using the zip
> function, kinda like
> 
> def pad(*iterables):
>     max_length = 0
>     for each_iterable in iterables:
>         if len(each_iterable) > max_length: max_length =
> len(each_iterable)
>     for each_iterable in iterables:
>         each_iterable.extend([None for i in xrange(0,max_length-
> len(each_iterable))])
> 
> pad(array1, array2, array3)
> for i in zip(array1, array2, array3):
>     print i
> 

Another option is to pad each iterator as it is exhausted. That way you 
can use any iterators not just lists. e.g.

from itertools import cycle, chain

def paddedzip(*args, **kw):
    padding = kw.get('padding', '')
    def generate_padding():
        padders = []
        def padder():
            if len(padders) < len(args)-1:
                padders.append(None)
                while 1:
                    yield padding
        while 1:
            yield padder()

    return zip(*(chain(it, pad) 
        for (it, pad) in zip(args, generate_padding())))

for i in paddedzip(xrange(10), ['one', 'two', 'three', 'four'],
                   ['a', 'b', 'c'], padding='*'):
    print i