CODEWITHSUNDEEP
pythonarrays
Zeusbeer
Zeusbeer

Reputation: 89

How do I find the position of the first 0 looking backwards in a numpy array?

Let's say I have a really long array like this:

arr = np.array([0,0,1,1,0,1,1,1,0,0,0,1,1,0,0,1]}

I also have a maximum position where I can look, like 6, making a slice of the array that returns this:

sliceLocation = 6

returning:

np.array([0,0,1,1,0,1,1]}

now I want to write a piece of code that slices the array and then searches for the first 0 inside this array coming from the back, in this case returning 4 as a viable position in a quick and efficient time. Can anybody help me?

Upvotes: 0

Views: 185

Answers (2)

IoaTzimas
IoaTzimas

Reputation: 10624

The following should work:

sliceLocation = 6
sliceLocation-list(arr)[:sliceLocation+1][::-1].index(0)

4

How it works: It slices the array, changes it to a list, reverses it, find the index of first 0 and by subtracting it from sliceLocation it gives the final result

Upvotes: 0

campy
campy

Reputation: 86

Here is your example but i dont understand what you want to do with the rest of the array arr.

arr = np.array([0,0,1,1,0,1,1,1,0,0,0,1,1,0,0,1])
sliceLocation = 6

arr = arr[:sliceLocation+1]
idx = np.where(arr==0)[0][-1]

idx = 4

Upvotes: 1

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