First Occurrence of True Number in Python

In this article we are required to find the first occurring non-zero number in a given list of numbers.

With enumerate and next

We sue enumerate to get the list of all the elements and then apply the next function to get the first non zero element.

Example

 Live Demo

listA = [0,0,13,4,17]
# Given list
print("Given list:\n " ,listA)
# using enumerate
res = next((i for i, j in enumerate(listA) if j), None)
# printing result
print("The first non zero number is at: \n",res)

Output

Running the above code gives us the following result −

Given list:
[0, 0, 13, 4, 17]
The first non zero number is at:
2

With next and filter

The next and filter conditions are applied to the elements of the list along with lambda expression with a condition not equal to zero.

Example

listA = [0,0,13,4,17]
# Given list
print("Given list:\n " ,listA)
# using next,filetr and lambda
res = listA.index(next(filter(lambda i: i != 0, listA)))
# printing result
print("The first non zero number is at: \n",res)

Output

Running the above code gives us the following result −

Given list:
[0, 0, 13, 4, 17]
The first non zero number is at:
2