Python itertools.repeat Function

The itertools.repeat function in Python’s itertools module returns an iterator that repeats a single value infinitely or a specified number of times. It is useful for generating constant sequences or combining with other iterators.

Table of Contents

1. Introduction
2. itertools.repeat Function Syntax
3. Examples
   • Basic Usage
   • Specifying the Number of Repeats
   • Using repeat with map
   • Combining repeat with Other Itertools Functions
4. Real-World Use Case
5. Conclusion

Introduction

The itertools.repeat function creates an iterator that repeats a given value indefinitely or for a specified number of times. This can be useful for tasks that require a constant sequence or when you need to pair a single value with each item in another iterable.

itertools.repeat Function Syntax

Here is how you use the itertools.repeat function:

import itertools

iterator = itertools.repeat(object, times=None)

Parameters:

• object: The value to be repeated.
• times: Optional. The number of times to repeat the value. If not specified, the value is repeated indefinitely.

Returns:

• An iterator that repeats the given value.

Examples

Basic Usage

Create an iterator that repeats a value indefinitely.

Example

import itertools

repeat_iterator = itertools.repeat('A')
for _ in range(5):
    print(next(repeat_iterator), end=' ')

Output:

A A A A A 

Specifying the Number of Repeats

Create an iterator that repeats a value a specific number of times.

Example

import itertools

repeat_iterator = itertools.repeat('B', times=3)
for item in repeat_iterator:
    print(item, end=' ')

Output:

B B B 

Using repeat with map

Combine repeat with map to apply a function to a constant value paired with each item in another iterable.

Example

import itertools

numbers = [1, 2, 3]
squares = map(pow, numbers, itertools.repeat(2))
print(list(squares))

Output:

[1, 4, 9]

Combining repeat with Other Itertools Functions

Use repeat with zip to pair a constant value with each item in another iterable.

Example

import itertools

letters = ['a', 'b', 'c']
paired = zip(itertools.repeat(1), letters)
print(list(paired))

Output:

[(1, 'a'), (1, 'b'), (1, 'c')]

Real-World Use Case

Filling a List with a Constant Value

Use repeat to initialize a list with a constant value.

Example

import itertools

constant_value_list = list(itertools.repeat(0, times=10))
print(constant_value_list)

Output:

[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

Conclusion

The itertools.repeat function is used for creating an iterator that repeats a value either indefinitely or a specified number of times. It is useful for generating constant sequences, initializing lists, and combining with other iterators for various tasks.