Python 3 int除法运算符返回浮点数吗？ [英] Python 3 int division operator is returning a float?

问题描述

在我的一项任务中，我遇到了一个奇怪的实现，我很好奇它是错误还是设计的行为。

In one of my assignments I came across a weird implementation, and I was curious if it's a bug or the designed behavior.

在Python 3中，除以 / 返回浮点数，而 // 表示整数除法，应返回整数。我发现尽管在整数除法时两个值中的任何一个都是浮点数，它将返回一个浮点数。

In Python 3, division by / returns a floating point number, and // means integer division and should return an integer. I've discovered though that if either of the values is a float when doing integer division, it will return a float.

示例：

# These all work as expected
10 / 2
-> 5.0
11 / 2
-> 5.5
10 // 2
-> 5
11 // 2
-> 5
# Here things start to get weird
10.0 // 2
-> 5.0
10 // 2.0
-> 5.0
11.0 // 2
-> 5.0

该应该表现为这种行为吗？如果是这样，为什么会这样运行？

Is this supposed to behave this way? If so, why does it behave this way?

推荐答案

来自 PEP-238 ，它引入了新的部门（重点是我的部门）：

From PEP-238, which introduced the new division (emphasis mine):

地板分割的语义

地板除法将在所有Python数值类型
中实现，并将具有以下语义：

Semantics of Floor Division

Floor division will be implemented in all the Python numeric types, and will have the semantics of:

a // b == floor(a/b)

除了结果类型将是 a 和$ b的通用类型$ b b 在操作之前被强制。

except that the result type will be the common type into which a and b are coerced before the operation.

具体来说，如果 a 和 b 是同一类型， a // b 也将是该类型。如果输入是不同类型，则它们首先是
使用与所有其他
算术运算符相同的规则强制转换为通用类型。

Specifically, if a and b are of the same type, a//b will be of that type too. If the inputs are of different types, they are first coerced to a common type using the same rules used for all other arithmetic operators.

尤其是，如果 a 和 b 均为整数或多头，则结果的
类型和值与这些类型的经典除法（对于混合输入类型，包括
； int // long 和 long // int 都会使
都返回一个long）。

In particular, if a and b are both ints or longs, the result has the same type and value as for classic division on these types (including the case of mixed input types; int//long and long//int will both return a long).

对于浮点输入，结果为浮点数。例如：

3.5//2.0 == 1.0

复数， // 引发异常，因为不允许
复数的 floor（） 。

For complex numbers, // raises an exception, since floor() of a complex number is not allowed.

对于用户定义的类和扩展类型，所有语义都取决于该类或类型的实现。

For user-defined classes and extension types, all semantics are up to the implementation of the class or type.

是的，它的行为应该是这样。 // 表示整数除法，应该返回整数 -不完全，它表示地板除法并应返回等于整数（您总是希望（a // b）.is_integer（）为真，其中任何一个操作数都是浮点数）。

So yes, it is supposed to behave that way. "// means integer division and should return an integer" - not quite, it means floor division and should return something equal to an integer (you'd always expect (a // b).is_integer() to be true where either operand is a float).

这篇关于Python 3 int除法运算符返回浮点数吗？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！