The range function from the xrange function

 

In Python, both range and xrange are used to generate a sequence of numbers, but they differ significantly in terms of their functionality and behavior. It’s important to note that xrange was available in Python 2, while range behaves differently in Python 3. Here are the key distinctions:

1. Return Type

– range: In Python 2, range returns a list containing all the numbers in the specified range. For example, range(5) produces [0, 1, 2, 3, 4].
– xrange: In Python 2, xrange returns an iterator that generates numbers on demand (lazily), which means it does not create a list in memory. This is more memory efficient for large ranges. For example, xrange(5) produces an xrange object that generates numbers from 0 to 4 on-the-fly.

2. Memory Usage

– range: Since range generates a complete list of numbers, it consumes more memory, especially with large ranges.
– xrange: As an iterator, xrange uses less memory because it generates each number one at a time and only when required.

3. Behavior in Python 3

– In Python 3, xrange has been removed completely. The range function in Python 3 behaves like xrange in Python 2; it returns an immutable sequence type that generates numbers on-the-fly rather than creating a full list. This means that in Python 3, you will always use range, which is efficient in terms of memory usage.

Examples

Python 2 Example

# Python 2
print(range(5)) # Output: [0, 1, 2, 3, 4]
print(xrange(5)) # Output: xrange(0, 5)

Python 3 Example

# Python 3
print(range(5)) # Output: range(0, 5) – behaves like xrange from Python 2

Summary

– Python 2:

– range: Returns a list.
– xrange: Returns an iterator (more memory efficient).

– Python 3:

– range: Functions like xrange from Python 2 (returns an immutable sequence).

When writing new code, it is recommended to use Python 3 and rely on the range function, as xrange is no longer available.