enumerate()

enumerate(iterable, start=0)

Returns: enumerate object · Updated March 13, 2026 · Built-in Functions

built-in iteration counter indexing

The enumerate() function takes an iterable and returns an enumerate object that yields pairs of (index, value) during iteration. It replaces the common pattern of manually initializing and incrementing a counter variable inside a loop, making code more readable and less error-prone.

Syntax

enumerate(iterable, start=0)

Parameters

Parameter	Type	Default	Description
`iterable`	iterable	—	Any object that supports iteration (list, tuple, string, dict, file object, generator, etc.)
`start`	`int`	`0`	The integer value from which to start counting. The first element will have index `start`, the second will have `start + 1`, and so on.

Returns: An enumerate object, which is a lazy iterator yielding tuples of (index, value). Convert to a list or tuple to materialize all pairs, or iterate directly.

Examples

Basic usage

The most common use case is iterating over a sequence while tracking the index:

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

for index, fruit in enumerate(fruits):
    print(f"{index}: {fruit}")
# 0: apple
# 1: banana
# 2: cherry

Custom start value

The start parameter lets you begin counting from any integer:

for rank, name in enumerate(["Alice", "Bob", "Charlie"], start=1):
    print(f"#{rank} {name}")
# #1 Alice
# #2 Bob
# #3 Charlie

This is particularly useful for 1-based indexing, human-readable output, and matching external data sources that use different indexing conventions.

Converting to a list of tuples

For scenarios requiring all index-value pairs at once:

letters = "abcde"
indexed = list(enumerate(letters))
print(indexed)
# [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd'), (4, 'e')]

Using with a tuple

Works with any iterable, not just lists:

point = (10, 20, 30)

for i, coord in enumerate(point):
    print(f"Dimension {i}: {coord}")
# Dimension 0: 10
# Dimension 1: 20
# Dimension 2: 30

Common Patterns

Processing file contents with line numbers

When reading files, enumerate() with start=1 provides natural line numbers:

with open("config.txt") as f:
    for line_num, line in enumerate(f, start=1):
        print(f"Line {line_num}: {line.strip()}")

Building a dictionary from a list

Create a mapping from values to their positions:

names = ["Alice", "Bob", "Charlie"]
name_to_index = {name: i for i, name in enumerate(names)}
print(name_to_index)
# {'Alice': 0, 'Bob': 1, 'Charlie': 2}

Enumerating in reverse

Combine with reversed() to iterate backwards while maintaining indices:

colors = ["red", "green", "blue"]

for i, color in reversed(list(enumerate(colors))):
    print(f"{i}: {color}")
# 2: blue
# 1: green
# 0: red

With list comprehension for transformation

Transform a list while preserving index information:

values = [10, 20, 30, 40]
doubled_with_index = [(i, v * 2) for i, v in enumerate(values)]
print(doubled_with_index)
# [(0, 20), (1, 40), (2, 60), (3, 80)]