CODEWITHSUNDEEP
pythonpython-3.x
Kaizer von Maanen
Kaizer von Maanen

Reputation: 987

Python: finding leftmost non-zero in list of lists

say I have this list of list

listlist = [[0,0,0,1],[0,0,1,1],[1,0,1,1]]

and a empty dict()

answer = dict()

and say I want to find the leftmost non-zero in each list such that I can save the index of that non-zero number into a dictionary like:

for list in listlist: #(this is how the first iteration would look like:)

answer[0] = 3

next iteration

answer[1] = 2

next iteration

answer[2] = 0

I am pretty new at programming, so excuse me if it is trivial, I have tried different stuff and it is hard to find out how to do this.

Upvotes: 2

Views: 358

Answers (3)

Stephan
Stephan

Reputation: 17991

Assuming only 0s and 1s this should work

i = 0
for mylist in listlist:
  answer[i] = mylist.index(1)
  i += 1

I recommend that you do not name your list list, that overrides some functionality. I prefer to default to the variable name mylist

Upvotes: 4

Jared
Jared

Reputation: 26407

If it's only ever 0s and 1s just do something like,

>>> answer = {i: lst.index(1) for i, lst in enumerate(listlist)}
>>> answer
{0: 3, 1: 2, 2: 0}

Also, don't use list as a variable name since it will mask list built-in.

Upvotes: 8

David.Zheng
David.Zheng

Reputation: 913

listlist = [[0,0,0,1],[0,0,1,1],[1,0,1,1]]
answer = dict()
for idx,alist in enumerate(listlist):
    for i in range(len(alist)):
        if alist[i] > 0:
            answer[idx] = i

Upvotes: 2

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