get index of first occurrence in list python code example

Example 1: get all occurrence indices in list python

a_list = [1, 2, 3, 1]

indices = []
for i in range(len(a_list)):
   if a_list[i] == 1:
      indices.append(i)

# more concise way
a_list = [1, 2, 3, 1]
indices = [index for index, element in enumerate(a_list) if element == 1]

Example 2: python find index of first matching element in a list

# Basic syntax:
list.index(element, start, end) 
# Where:
#	- Element is the item you're looking for in the list
# 	- Start is optional, and is the list index you want to start at
#	- End is option, and is the list index you want to stop searching at

# Note, Python is 0-indexed

# Example usage:
my_list = [1, 2, 3, 4, 5, 6, 7, 8, 42, 9, 10]
my_list.index(42)
--> 8

Example 3: python get first occurrence in list

next(obj for obj in objs if obj.val==5)