在Python中进行强制转换 [英] Casting vs. coercion in Python

问题描述

在Python文档和邮件列表中，我看到值有时是强制转换的，有时是强制的的。有什么不同？

In the Python documentation and on mailing lists I see that values are sometimes "cast", and sometimes "coerced". What is the difference?

推荐答案

我认为 casting不应该用于Python；只有类型转换，而没有强制转换（在C意义上）。完成类型转换，例如通过 int（o）将对象o转换为整数（实际上，整数对象是从o构造的）。强制转换发生在二进制操作的情况下：如果您执行 x + y ，并且x和y具有不同的类型，则在执行该操作之前将它们强制转换为单一类型。在2.x中，特殊方法 __ coerce __ 允许对象控制其强制。

I think "casting" shouldn't be used for Python; there are only type conversion, but no casts (in the C sense). A type conversion is done e.g. through int(o) where the object o is converted into an integer (actually, an integer object is constructed out of o). Coercion happens in the case of binary operations: if you do x+y, and x and y have different types, they are coerced into a single type before performing the operation. In 2.x, a special method __coerce__ allows object to control their coercion.

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