Python 3

操作 结果 笔记 X / y x和y的商 X // y x和y的底商 (1） 注: 也称为整数除法。结果值是一个整型，尽管结果的类型不一定是int。结果总是趋近于负无穷:1//2等于0，(-1)//2等于-1,1//(-2)等于-1，(-1)//(-2)等于0。

Python 2

Operation Result Notes x / y quotient of x and y (1) x // y (floored) quotient of x and y (4)(5) Notes: 1. For (plain or long) integer division, the result is an integer. The result is always rounded towards minus infinity: 1/2 is 0, (-1)/2 is -1, 1/(-2) is -1, and (-1)/(-2) is 0. Note that the result is a long integer if either operand is a long integer, regardless of the numeric value. 4. Deprecated since version 2.3: The floor division operator, the modulo operator, and the divmod() function are no longer defined for complex numbers. Instead, convert to a floating point number using the abs() function if appropriate. 5. Also referred to as integer division. The resultant value is a whole integer, though the result’s type is not necessarily int.

总结

x//y:精确的整数除法 int(x/y) OR math.floor(x/y):不精确的整数除法(但几乎正确) X /y:浮点除法(没有意义)

显著计算结果

import math
N = 1004291331219602346 # huge number 

print(N//100) #=> 10042913312196023 is correct answer
print(math.floor(N/100)) #=> 10042913312196024 is wrong answer
print(math.ceil(N/100)) #=> 10042913312196024 is wrong answer
print(int(N/100)) #=> 10042913312196024 is wrong answer

考虑

考虑int(x/y)的取值。 首先，Python计算表达式x/y并得到不精确的浮点数z。 其次，Python计算表达式int(z)。 当意义的丧失不可忽视时，我们会得到错误的结果。

>>> print 5.0 / 2
2.5

>>> print 5.0 // 2
2.0

前面的答案都很好。我想再补充一点。在某些情况下，它们会得到相同的商。之后，除法运算符(//)可以正常工作，但除法(/)运算符不行:

>>> int(755349677599789174 / 2) # Wrong answer
377674838799894592

>>> 755349677599789174 // 2     # Correct answer
377674838799894587

方程的答案四舍五入到下一个较小的整数或以。0作为小数点的浮点数。

>>>print 5//2
2
>>> print 5.0//2
2.0
>>>print 5//2.0
2.0
>>>print 5.0//2.0
2.0

Python 2。x澄清:

为Python阐明2。X线，/既不是层除法也不是真除法。

当两个参数都为int时，/为整除;但当其中一个参数为float时，/为真除法。