How Is Irange() Any Different From Range() Or Xrange()?

I was going through Python Generators Wiki when I came across this RangeGenerator page which talks about irange() - This will let us iterator over large spans of numbers without

Solution 1:

irange() returns a generator type, which can only be iterated over. Nothing else. Once you iterated over it, the generator is exhausted and can not be iterated over again.

The Python 2 xrange() type and Python 3 range() type are sequence types, they support various operations that other sequences support as well, such as reporting on their length, test for containment, and indexing:

>>>xr = xrange(10, 20, 3)>>>len(xr)
4
>>>10in xr
True
>>>xr[0]
10
>>>xr[1]
13

You can iterate over these objects more than once:

>>>for i in xr:...print i,... 
10 13 16 19
>>>for i in xr:...print i,... 
10 13 16 19

You can even use the reversed() function to iterate over them in reverse, efficiently:

>>>for i inreversed(xr):...print i,... 
19 16 13 10

The Python 3 range() type is an improved version of xrange(), in that it supports more sequence operations, is more efficient still, and can handle values beyond sys.maxint (what would be a long integer in Python 2).

It supports slicing, for example, which results in a newrange() object for the sliced values:

>>>r = range(10, 20, 3)>>>r[:2]
range(10, 16, 3)

You can use negative indices just like you can with other Python sequences, to get elements counting from the end:

>>>r[-2]
16
>>>r[-2:]
range(16, 22, 3)

and the type supports testing for equality; two range() instances are equal if they'd yield the same values:

>>> range(10, 20, 3) == range(10, 21, 3)
True

In Python 2, the only advantage the generator irange() might have is that it doesn't suffer from the limitation to non-long integers that xrange() is subjected to:

>>> import sys
>>> xrange(sys.maxint)
xrange(9223372036854775807)
>>> xrange(sys.maxint + 1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OverflowError: Python int too large to convert to C long

Solution 2:

irange provides an generator which does not loads entire result into memory. Say you have range(1, 1000000) in case a list of 1000000 numbers would be loaded into memory, whereas in case of xrange(1, 1000000), just one number would be in memory at a time.