[Find Index of First Non-zero Occurrence] #numpy #nonzero

find_index_of_first_nonzero_occurrence.py

import numpy as np

def find_index_of_first_nonzero_occurrence(array):
    """
    Find the index of the first non-zero occurrence in a numpy array.
    This is essentially a wrapper around np.flatnonzero(). If there are 
    no non-zero values None is returned. 
    
    array (numpy array): Should be 1d array and all elements should be numeric
    """
    try:
        first_occurance_index = np.flatnonzero(array)[0]
    except IndexError as err:
        if err.args[0] == 'index 0 is out of bounds for axis 0 with size 0':
            # No non-zero values are present
            first_occurance_index = None
        else:
            # Index error from other causes(?) are passed through
            raise IndexError(err)
    
    return first_occurance_index