Hold an object, using class in python

Question

I write a program to weave lists of floats together, for example:

l1 = [5.4, 4.5, 8.7]
l2 = [6.5, 7.8]
l3 = [6.7, 6.9]

I want to weave l1 into

Answer 1

Your weave function drops the last element of l2; you need to use itertools.zip_longest() here:

try:
    from itertools import zip_longest
except ImportError:
    # Python 2
    from itertools import izip_longest as zip_longest

def weave_rows(row1, row2):
    return [v for v in sum(zip_longest(row1, row2), ()) if v is not None]

Note that you need to return, not print, your output. The izip_longest() call adds None placeholders, which we need to remove again from the sum() output after zipping.

Now you can simply weave in a 3rd list into the output of the previous two:

weave(weave(l1, l2), l3)

Demo:

>>> weave_rows(l1, l2)
[5.4, 6.5, 4.5, 7.8, 8.7]
>>> weave_rows(weave_rows(l1, l2), l3)
[5.4, 6.7, 6.5, 6.9, 4.5, 7.8, 8.7]