Python 的 coerce() 是做什么用的?

问题描述

Python 内置的 coerce 函数有哪些常见用途?如果我不知道数值 type ，我可以看到应用它"noreferrer">根据文档，但是否存在其他常见用法?我猜想在执行算术计算时也会调用 coerce()，例如 x = 1.0 +2.它是一个内置函数，所以大概它有一些潜在的常见用法?

What are common uses for Python's built-in coerce function? I can see applying it if I do not know the type of a numeric value as per the documentation, but do other common usages exist? I would guess that coerce() is also called when performing arithmetic computations, e.g. x = 1.0 +2. It's a built-in function, so presumably it has some potential common usage?

推荐答案

它是 早期的python，它基本上使一个数字元组成为相同的底层数字类型，例如

Its a left over from early python, it basically makes a tuple of numbers to be the same underlying number type e.g.

>>> type(10)
<type 'int'>
>>> type(10.0101010)
<type 'float'>
>>> nums = coerce(10, 10.001010)
>>> type(nums[0])
<type 'float'>
>>> type(nums[1])
<type 'float'>

这也是为了让对象在旧类中表现得像数字
(在这里使用它的一个不好的例子是......)

It is also to allow objects to act like numbers with old classes
(a bad example of its usage here would be ...)

>>> class bad:
...     """ Dont do this, even if coerce was a good idea this simply
...         makes itself int ignoring type of other ! """
...     def __init__(self, s):
...             self.s = s
...     def __coerce__(self, other):
...             return (other, int(self.s))
... 
>>> coerce(10, bad("102"))
(102, 10)

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