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

range creates a list, so if you do range(1, 10000000) it creates a list in memory with 9999999 elements.

xrange is a generator, so it is a sequence object is a that evaluates lazily.

This is true, but in Python 3, range() will be implemented by the Python 2 xrange(). If you need to actually generate the list, you will need to do:

list(range(1,100))

In Python 2.x:

• range creates a list, so if you do range(1, 10000000) it creates a list in memory with 9999999 elements.

• xrange is a sequence object that evaluates lazily.

In Python 3:

• range does the equivalent of Python 2's xrange. To get the list, you have to explicitly use list(range(...)).
• xrange no longer exists.

Remember, use the timeit module to test which of small snippets of code is faster!

$ python -m timeit 'for i in range(1000000):' ' pass'
10 loops, best of 3: 90.5 msec per loop
$ python -m timeit 'for i in xrange(1000000):' ' pass'
10 loops, best of 3: 51.1 msec per loop

Personally, I always use range(), unless I were dealing with really huge lists -- as you can see, time-wise, for a list of a million entries, the extra overhead is only 0.04 seconds. And as Corey points out, in Python 3.0 xrange() will go away and range() will give you nice iterator behavior anyway.