不同之处在于 int 类型的实现。 Python 3.x仅使用任意大小的整数类型（在2.x中为 long ），而在Python 2.x中，其值最高为 sys .maxint 使用更简单的 int 类型，该类型在引擎盖下使用简单的C long

The difference is in the implementation of the int type. Python 3.x uses the arbitrary-sized integer type (long in 2.x) exclusively, while in Python 2.x for values up to sys.maxint a simpler int type is used that uses a simple C long under the hood.

一旦将循环限制为 long 个整数，Python 3.x是更快：

Once you limit your loops to long integers, Python 3.x is faster:

>>> from timeit import timeit
>>> MAX_NUM = 3*10**3
>>> def bar():
...     i = MAX_NUM + sys.maxsize
...     while i > sys.maxsize:
...         i -= 1
... 

Python 2：

>>> timeit(bar, number=10000)
5.704327821731567

Python 3：

>>> timeit(bar, number=10000)
3.7299320790334605

我用过 sys.maxsize 作为 sys.maxint 从Python 3中删除的，但整数值基本相同。

I used sys.maxsize as sys.maxint was dropped from Python 3, but the integer value is basically the same.

因此，Python 2的速度差异仅限于第一个（2 ** 63）-64位为1个整数，（2 ** 31）-32位系统为1个整数。

The speed difference in Python 2 is thus limited to the first (2 ** 63) - 1 integers on 64-bit, (2 ** 31) - 1 integers on 32 bit systems.

由于不能在 xrange（）上使用 long 类型Python 2，我没有对该函数进行比较。

Since you cannot use the long type with xrange() on Python 2, I did not include a comparison for that function.