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

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.

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))

xrange only stores the range params and generates the numbers on demand. However the C implementation of Python currently restricts its args to C longs:

xrange(2**32-1, 2**32+1)  # When long is 32 bits, OverflowError: Python int too large to convert to C long
range(2**32-1, 2**32+1)   # OK --> [4294967295L, 4294967296L]

Note that in Python 3.0 there is only range and it behaves like the 2.x xrange but without the limitations on minimum and maximum end points.

xrange returns an iterator and only keeps one number in memory at a time. range keeps the entire list of numbers in memory.