How to delete items from a list if an item in another list is equal to 0?

Question

I have 3 lists, radius, x, and y. Each one is the same length. I want to delete the 'i'th item from each list if the 'i'th item in radius is equal to 0. Below is the code I am trying to use, but for some reason is not working. Thank you in advance!

for i in range(len(radius)):
    if radius[i]==0:
        radius.remove(i)
        x.remove(i)
        y.remove(i)

In the argument of remove, you give the actual item, not item index. Use del — Ejaz, Jun 10 '16 at 15:32

michael_j_ward · Answer 1 · 2016-06-10T15:37:01.113

1

have you tried?

Breaking this down will give you a good understanding of python variable unpacking, list comprehensions, and how zip works.

x,y, radius = zip(*[(i,j,r) for i,j,r in zip(x,y,radius) if r != 0])

edited Jun 10 '16 at 15:37

answered Jun 10 '16 at 15:31

michael_j_ward

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score 1 · Answer 2 · answered Jun 10 '16 at 15:32

1

You could use list.index to get the index of the 0 element in radius and then just delete it from radius, x and y:

radius = [1, 2, 3, 4, 5, 0, 2]
x = [2, 3, 4, 5, 6, 7, 8]
y = [8, 7, 6, 5, 4, 3, 2]

index = radius.index(0)

Now that you have the index, delete:

del radius[index], x[index], y[index]

If many zeros exist, you could incorporate this in a loop with a try-catch to break if index cannot find another 0.

answered Jun 10 '16 at 15:32

Dimitris Fasarakis Hilliard

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1

This should work, too, but it has quadratic complexity. – tobias_k Jun 10 '16 at 15:36

score 0 · Answer 3 · answered Jun 10 '16 at 15:34

0

This would be a good case for a list comprehension:

In [1]: x, y, r = [1,2,3,4], [1,2,3,4], [1,0,1,0]

In [2]: x, y, r = zip(*[xyr_i for xyr_i in zip(x,y,r) if xyr_i[2] != 0])

In [3]: print(x)
(1, 3)

In [4]: print(y)
(1, 3)

In [5]: print(r)
(1, 1)

answered Jun 10 '16 at 15:34

evan.oman

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How to delete items from a list if an item in another list is equal to 0?

3 Answers3