Get indices of True values in a binary list in Python

When a Python list contains values like true or false and 0 or 1 it is called binary list. In this article we will take a binary list and find out the index of the positions where the list element is true.

With enumerate

The enumerate function extracts all the elements form the list. We apply a in condition to check of the extracted value is true or not.

Example

listA = [True, False, 1, False, 0, True]
# printing original list
print("The original list is :\n ",listA)
# using enumerate()
res = [i for i, val in enumerate(listA) if val]
# printing result
print("The indices having True values:\n ",res)

Output

Running the above code gives us the following result −

The original list is :
[True, False, 1, False, 0, True]
The indices having True values:
[0, 2, 5]

With compress

Using compress we iterate through each of the element in the list. This brings out only the elements whose value is true.

Example

from itertools import compress
listA = [True, False, 1, False, 0, True]
# printing original list
print("The original list is :\n ",listA)
# using compress()
res = list(compress(range(len(listA)), listA))
# printing result
print("The indices having True values:\n ",res)

Output

Running the above code gives us the following result −

The original list is :
[True, False, 1, False, 0, True]
The indices having True values:
[0, 2, 5]