如何使用Python 2中的旧列表创建包含特定项目的新列表？

Question

I have a list of lists (I think) that looks like this:

[['Cats', 'Dogs', '', 'Gerbils'],
['Tigers', 'Snakes', '', 'Hamsters'],
['Iguanas', 'Snails', '', 'Worms']]

I need to build a new list of lists by ignoring the blank fields. So my new lists would look like this:

[['Cats', 'Dogs', 'Gerbils'],
['Tigers', 'Snakes', 'Hamsters'],
['Iguanas', 'Snails','Worms']]

I've not got a deep understanding of lists in Python so I'm at a complete loss as to how to do this. Can anyone point me to doc that will show me the way?

Thanks!

Edit: list-of-lists syntax corrected by Dan

Answer 1

l = [['Cats', 'Dogs', '', 'Gerbils'],
     ['Tigers', 'Snakes', '', 'Hamsters'],
     ['Iguanas', 'Snails', '', 'Worms']]

[[i for i in sub if i] for sub in l]

Output

[['Cats', 'Dogs', 'Gerbils'],
 ['Tigers', 'Snakes', 'Hamsters'],
 ['Iguanas', 'Snails', 'Worms']]

Answer 2

newlist = [ filter(None, x) for x in oldlist ]

Edited in response to comments:

It is arguable that using filter(bool, x) is more readable than filter(None, x) . In effect they are the same, both meaning "filter out the items that are false/None/empty/zero".

In python 3, filter returns an iterable object rather than a list, so the equivalent would be

newlist = [ list(filter(None, x)) for x in oldlist ]

or

newlist = [ list(filter(bool, x)) for x in oldlist ]

each of which is equivalent to

[ [ item for item in x if item ] for x in oldlist ]