Python: 探究py2與py3除法的區別

起因

在用python2解釋器運行python3代碼的時候，出現了bug。debug後發現是因爲python3中的/ 原本表示 精確除法，卻被python2解釋器解釋成了 地板除，最終導致了錯誤。因此我上網查閱了相關資料，並總結如下表：

總結

version	/	//
py2	整數除法時爲地板除，浮點數除法時爲精確除	地板除
py3	精確除法	地板除

Test

x = y = 10
x /= 2    # 精確除
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
>>> 

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