Function grouper

官方samples/common.py:202–209

grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx

(n, iterable, fillvalue=None)

def grouper(n, iterable, fillvalue=None):
    '''grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx'''
    args = [iter(iterable)] * n
    if PY3:
        output = it.zip_longest(fillvalue=fillvalue, *args)
    else:
        output = it.izip_longest(fillvalue=fillvalue, *args)
    return output

def mosaic(w, imgs):
    '''Make a grid from images.