Python - zip only lists that contain data

Question

I have a script that converts data from one type to another. The source file can have one, two or all of: position, rotation and scale data.

My script zips the 3 together after conversions have taken place for the output file.

In this case, my source file only contains position data. So the lists returned at the end are:

pData = [['-300.2', '600.5'],['150.12', '280.7'],['19.19', '286.56']]
rData = []
sData = []

translationData = list(zip(pData, rData, sData))

If I try this, it will return [] because the shortest list is []. If I try:

translationData = list(zip_longest(pData, rData, sData))

I get:

`[(['-300.2', '600.5'], None, None), (['150.12', '280.7'], None, None), (['19.19', '286.56'], None, None)]`

Is there any way to only zip lists that contain data, or remove the None's from within the tuples within the list?

Thanks in advance!

Answer 1

You can use the filter builtin embedded in a list-comp.

Note: In Python 3 filter returns an iterator, so you will need to call tuple() on it. (unlike in py2)

pData = [['-300.2', '600.5'],['150.12', '280.7'],['19.19', '286.56']]
rData = []
sData = []

from itertools import zip_longest  # izip_longest for python 2
[tuple(filter(None, col)) for col in zip_longest(pData, rData, sData)]

Result:

[(['-300.2', '600.5'],), (['150.12', '280.7'],), (['19.19', '286.56'],)]