Python enumerate() Function

The enumerate() function in Python is used to loop through a sequence (like a list, tuple, or string) while keeping track of the index of the current item.

It's a clean and Pythonic way to write loops when you need both index and value.

Syntax

enumerate(iterable, start=0)

Parameters:

• iterable – A sequence like a list, tuple, or string
• start – The index to start counting from (default is 0)

Returns:

• An enumerate object which can be used in a loop to get (index, value) pairs

Basic Example

fruits = ["apple", "banana", "cherry"]

for index, fruit in enumerate(fruits):
    print(index, fruit)

0 apple
1 banana
2 cherry

Example: Start Counting from 1

for index, fruit in enumerate(fruits, start=1):
    print(index, fruit)

1 apple
2 banana
3 cherry

Use Case: Replacing Manual Counter in Loops

Instead of writing:

i = 0
for item in fruits:
    print(i, item)
    i += 1

You can simplify it using enumerate():

for i, item in enumerate(fruits):
    print(i, item)

Use Case: Working with Strings

for i, char in enumerate("hello"):
    print(f"Index {i} has character '{char}'")

Index 0 has character 'h'
Index 1 has character 'e'
Index 2 has character 'l'
Index 3 has character 'l'
Index 4 has character 'o'

Common Mistake

• Beginners often forget to unpack both index and value from enumerate(). Always use: for i, val in enumerate(...)

Interview Tip

enumerate() is often preferred in interviews over manually tracking counters in loops. It shows clean, Pythonic style.

Summary

• enumerate() helps track both index and item while looping.
• You can change the starting index using the start argument.
• Useful for iterating through lists, strings, or any iterable.

Practice Problem

Write a program that takes a list of names and prints them numbered from 1:

names = ["Alice", "Bob", "Charlie"]
for i, name in enumerate(names, start=1):
    print(f"{i}. {name}")

Expected Output:

1. Alice
2. Bob
3. Charlie