Assignment Versus Equality

[Lawrence D’Oliveiro]

On Wednesday, June 29, 2016 at 6:46:04 PM UTC+12, Steven D'Aprano wrote:
> On Wednesday 29 June 2016 15:51, Lawrence D’Oliveiro wrote:
> 
>> On Wednesday, June 29, 2016 at 5:26:46 PM UTC+12, Steven D'Aprano wrote:
>>> BUT in Python 3, the distinction between int and long is gone by dropping
>>> int and renaming long as "int". So all Python ints are BIGNUMs.
>> 
>> I don’t understand what the problem is with this. Is there supposed to be
>> some issue with performance? Because I can’t see it.
> 
> If there is a performance hit, it's probably pretty small. It may have been 
> bigger back in Python 3.0 or 3.1.
> 
> [steve at ando ~]$ python2.7 -m timeit -s "n = 0" "for i in xrange(10000): n += i"
> 100 loops, best of 3: 1.87 msec per loop
> 
> [steve at ando ~]$ python3.3 -m timeit -s "n = 0" "for i in range(10000): n += i"
> 1000 loops, best of 3: 1.89 msec per loop

Here is what I tried:

    ldo at theon:python_try> python2 int_speed_test.py
    2 ** 6 is 2 ** 6: True
    1000000 iterations of “a = 2 ** 6 // 2 ** 4” took 0.0624719s = 6.24719e-08s/iteration
    2 ** 9 is 2 ** 9: False
    1000000 iterations of “a = 2 ** 9 // 2 ** 6” took 0.0506701s = 5.06701e-08s/iteration
    2 ** 20 is 2 ** 20: False
    1000000 iterations of “a = 2 ** 20 // 2 ** 12” took 0.0441589s = 4.41589e-08s/iteration
    2 ** 64 is 2 ** 64: False
    1000000 iterations of “a = 2 ** 64 // 2 ** 32” took 0.138092s = 1.38092e-07s/iteration
    2 ** 96 is 2 ** 96: False
    1000000 iterations of “a = 2 ** 96 // 2 ** 64” took 0.1142s = 1.142e-07s/iteration
    ldo at theon:python_try> python3 int_speed_test.py
    2 ** 6 is 2 ** 6: True
    1000000 iterations of “a = 2 ** 6 // 2 ** 4” took 0.0230309s = 2.30309e-08s/iteration
    2 ** 9 is 2 ** 9: False
    1000000 iterations of “a = 2 ** 9 // 2 ** 6” took 0.0231234s = 2.31234e-08s/iteration
    2 ** 20 is 2 ** 20: False
    1000000 iterations of “a = 2 ** 20 // 2 ** 12” took 0.020053s = 2.0053e-08s/iteration
    2 ** 64 is 2 ** 64: False
    1000000 iterations of “a = 2 ** 64 // 2 ** 32” took 0.0182259s = 1.82259e-08s/iteration
    2 ** 96 is 2 ** 96: False
    1000000 iterations of “a = 2 ** 96 // 2 ** 64” took 0.0173797s = 1.73797e-08s/iteration

As you can see, Python 3 is actually *faster* than Python 2, particularly with smaller-magnitude integers.