[python] Why is there no xrange function in Python3?

Recently I started using Python3 and it's lack of xrange hurts.

Simple example:

1) Python2:

from time import time as t
def count():
  st = t()
  [x for x in xrange(10000000) if x%4 == 0]
  et = t()
  print et-st
count()

2) Python3:

from time import time as t

def xrange(x):

    return iter(range(x))

def count():
    st = t()
    [x for x in xrange(10000000) if x%4 == 0]
    et = t()
    print (et-st)
count()

The results are, respectively:

1) 1.53888392448 2) 3.215819835662842

Why is that? I mean, why xrange's been removed? It's such a great tool to learn. For the beginners, just like myself, like we all were at some point. Why remove it? Can somebody point me to the proper PEP, I can't find it.

Cheers.

Python 3's range type works just like Python 2's xrange. I'm not sure why you're seeing a slowdown, since the iterator returned by your xrange function is exactly what you'd get if you iterated over range directly.

I'm not able to reproduce the slowdown on my system. Here's how I tested:

Python 2, with xrange:

Python 2.7.3 (default, Apr 10 2012, 23:24:47) [MSC v.1500 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> import timeit
>>> timeit.timeit("[x for x in xrange(1000000) if x%4]",number=100)
18.631936646865853

Python 3, with range is a tiny bit faster:

Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 10:57:17) [MSC v.1600 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> import timeit
>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)
17.31399508687869

I recently learned that Python 3's range type has some other neat features, such as support for slicing: range(10,100,2)[5:25:5] is range(20, 60, 10)!

comp:~$ python Python 2.7.6 (default, Jun 22 2015, 17:58:13) [GCC 4.8.2] on linux2

>>> import timeit
>>> timeit.timeit("[x for x in xrange(1000000) if x%4]",number=100)

5.656799077987671

>>> timeit.timeit("[x for x in xrange(1000000) if x%4]",number=100)

5.579368829727173

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

21.54827117919922

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

22.014557123184204

With timeit number=1 param:

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=1)

0.2245171070098877

>>> timeit.timeit("[x for x in xrange(1000000) if x%4]",number=1)

0.10750913619995117

comp:~$ python3 Python 3.4.3 (default, Oct 14 2015, 20:28:29) [GCC 4.8.4] on linux

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

9.113872020003328

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=100)

9.07014398300089

With timeit number=1,2,3,4 param works quick and in linear way:

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=1)

0.09329321900440846

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=2)

0.18501482300052885

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=3)

0.2703447980020428

>>> timeit.timeit("[x for x in range(1000000) if x%4]",number=4)

0.36209142999723554

So it seems if we measure 1 running loop cycle like timeit.timeit("[x for x in range(1000000) if x%4]",number=1) (as we actually use in real code) python3 works quick enough, but in repeated loops python 2 xrange() wins in speed against range() from python 3.

Python3's range is Python2's xrange. There's no need to wrap an iter around it. To get an actual list in Python3, you need to use list(range(...))

If you want something that works with Python2 and Python3, try this

try:
    xrange
except NameError:
    xrange = range

One way to fix up your python2 code is:

import sys

if sys.version_info >= (3, 0):
    def xrange(*args, **kwargs):
        return iter(range(*args, **kwargs))

xrange from Python 2 is a generator and implements iterator while range is just a function. In Python3 I don't know why was dropped off the xrange.