Only nonzero values Python list

Question

I want to Extract only nonzero numbers from python list . This is what I am doing . but it isnt working it seems .

d=[num if num for num in d]

where d is my original list and again I want output in same list

Answer 1

In [5]: d =[1,2,3,0,0,9]

In [6]: d = filter(None,d) 

In [7]: d
Out[7]: [1, 2, 3, 9]

Some timings:

In [30]: %timeit filter(None,d)
1000000 loops, best of 3: 727 ns per loop

In [31]: %timeit filter(lambda x: x != 0, d)
100000 loops, best of 3: 3.89 µs per loop

In [32]: %timeit [x for x in d if x != 0]
100000 loops, best of 3: 2.33 µs per loop

In [33]: %timeit  [num for num in d if num]
100000 loops, best of 3: 2.04 µs per loop

As you only have numbers in your list filter(None,d) will work fine. If you had any other falsey values like empty lists [] etc.. it would also remove them.