What is the difference between "range" and "xrange" in Python 2?

Question

Jayant Kumar · Accepted Answer

Table of Contents
Introduction
In Python 2, range and xrange are functions used to generate sequences of numbers, commonly used in loops and iterations. While they appear similar, they have significant differences in terms of memory usage and performance. This article explains the differences between range and xrange, detailing their functionalities and providing practical examples.
Key Differences Between range and xrange
1. Memory Usage

**range**: In Python 2, range returns a list of integers. This means that it creates an entire list in memory containing all the numbers in the specified range. For large ranges, this can consume significant memory.
**xrange**: xrange returns an xrange object, which is an iterator that generates numbers on-the-fly as you iterate over it. This approach is more memory-efficient because it does not create the entire list in memory.

Example:
# Using range in Python 2
r = range(1, 1000000)  # Creates a list of 999,999 numbers
print(type(r))  # Output: &#x3C;type 'list'>

# Using xrange in Python 2
xr = xrange(1, 1000000)  # Creates an xrange object, not a list
print(type(xr))  # Output: &#x3C;type 'xrange'>

2. Performance

**range**: Since range generates a list, the creation of this list can be slow for large ranges. Additionally, operations on the list, such as indexing, can be faster compared to xrange due to its list-based nature.
**xrange**: xrange is designed for better performance with large ranges as it generates numbers lazily and uses less memory. Iterating over xrange objects is generally faster for large ranges.

Example:
# Timing range vs xrange
import time

start_time = time.time()
list(range(1, 1000000))  # Measure time to create a large list
print("Range time:", time.time() - start_time)

start_time = time.time()
list(xrange(1, 1000000))  # Measure time to convert xrange to list
print("Xrange time:", time.time() - start_time)

3. Usage in Loops

**range**: Suitable for loops where you need a list of numbers and may perform operations that require list indexing.
**xrange**: Preferred for loops where memory efficiency is important and only iteration is needed. xrange is often used in loops where the entire sequence of numbers does not need to be stored.

Example:
# Using range in a loop
for i in range(5):
    print(i)  # Output: 0, 1, 2, 3, 4

# Using xrange in a loop
for i in xrange(5):
    print(i)  # Output: 0, 1, 2, 3, 4

Practical Examples
Example : Memory Efficiency
# Using xrange to handle large ranges efficiently
for i in xrange(1000000):
    if i == 999999:
        print("Reached the end efficiently.")

Example : List Operations with Range
# Using range for operations that require a list
r = range(10)
print(r[5])  # Output: 5 (direct indexing is possible)

Conclusion
In Python 2, range and xrange both generate sequences of numbers, but they differ significantly in terms of memory usage and performance. range returns a list and is more suited for scenarios where the entire list is needed, while xrange provides a memory-efficient iterator and is ideal for large ranges where only iteration is required. Understanding these differences helps in choosing the appropriate function based on the needs of your program.

What is the difference between "range" and "xrange" in Python 2?

Table of Contents

Introduction

Key Differences Between `range` and `xrange`

1. Memory Usage

Example:

2. Performance

Example:

3. Usage in Loops

Example:

Practical Examples

Example : Memory Efficiency

Example : List Operations with Range

Conclusion

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