Find letter occurrences in a string
Input
find_indices('abracadabra', 'a')
Output
[0, 3, 5, 7, 10]
Returns each index where 'a' occurs in the string.
Full lesson preview
Use enumerate to track positions
Find all positions of a target value in any iterable using enumerate for efficient index tracking.
Python practice16 minModules & Standard LibraryIntermediateLast updated March 23, 2026
Problem statement
Given an iterable (string, list, tuple, etc.) and a target value, return a list of all indices where an element equals the target (using ==). Indices should be in ascending order. If the target is not present, return an empty list. Use enumerate to iterate with indices.
Task
Write a function that returns the list of indices where the target appears in the iterable, using enumerate.
Examples
Input format
A call: find_indices(iterable, target). The iterable may be any iterable type (string, list, tuple, etc.).
Output format
A list of integer indices where elements equal the target value.
Constraints
Use enumerate to get index and value in a single pass. Equality uses Python's == operator.
Samples
Sample 1
Input
find_indices([1, 2, 3, 2, 1], 2)
Output
[1, 3]
Indices of value 2 in the list are 1 and 3.