Python: 探究py2与py3除法的区别

起因

在用python2解释器运行python3代码的时候，出现了bug。debug后发现是因为python3中的/ 原本表示 精确除法，却被python2解释器解释成了 地板除，最终导致了错误。因此我上网查阅了相关资料，并总结如下表：

总结

version	/	//
py2	整数除法时为地板除，浮点数除法时为精确除	地板除
py3	精确除法	地板除

Test

x = y = 10
x /= 2    # 精确除
y //= 2    # 地板除
print(x, type(x))    # 5.0 <class 'float'>
print(y, type(y))    # 5 <class 'int'>

user@user:~$ python
Python 2.7.13 |Anaconda 2.4.1 (64-bit)| (default, Dec 20 2016, 23:09:15)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
Anaconda is brought to you by Continuum Analytics.
Please check out: http://continuum.io/thanks and https://anaconda.org >>> 9/2
4
>>> 9.0/2
4.5
>>> 9//2
4
>>> 9.0//2
4.0
>>> float(9)/2
4.5
>>> from __future__ import division
>>> 9/2
4.5
>>>
>>>
[3]+  Stopped                 python
>>>
>>>
user@user:~$ python3
Python 3.4.3 (default, Nov 17 2016, 01:08:31)
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 9/2
4.5
>>> 9//2
4
>>> 9.0//2
4.0
>>>