What is the difference between range and xrange functions in Python 2.X?

Question

Apparently xrange is faster but I have no idea why it\'s faster (and no proof besides the anecdotal so far that it is faster) or what besides that is different about

Answer 1

range() in Python 2.x

This function is essentially the old range() function that was available in Python 2.x and returns an instance of a list object that contains the elements in the specified range.

However, this implementation is too inefficient when it comes to initialise a list with a range of numbers. For example, for i in range(1000000) would be a very expensive command to execute, both in terms of memory and time usage as it requires the storage of this list into the memory.

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range() in Python 3.x and xrange() in Python 2.x

Python 3.x introduced a newer implementation of range() (while the newer implementation was already available in Python 2.x through the xrange() function).

The range() exploits a strategy known as lazy evaluation. Instead of creating a huge list of elements in range, the newer implementation introduces the class range, a lightweight object that represents the required elements in the given range, without storing them explicitly in memory (this might sound like generators but the concept of lazy evaluation is different).

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As an example, consider the following:

# Python 2.x
>>> a = range(10)
>>> type(a)

>>> b = xrange(10)
>>> type(b)

and

# Python 3.x
>>> a = range(10)
>>> type(a)