为什么要隐式检查Python中的空度? [英] Why implicitly check for emptiness in Python?

问题描述

Python的禅宗说显式比隐式好.

The Zen of Python says that explicit is better than implicit.

但是检查集合c是否为空的Python方式是:

Yet the Pythonic way of checking a collection c for emptiness is:

if not c:
    # ...

，然后检查集合是否不为空

and checking if a collection is not empty is done like:

if c:
    # ...

同上用于任何可能具有零"或空"(元组，整数，字符串，无等)的

ditto for anything that can have "zeroness" or "emptiness" (tuples, integers, strings, None, etc)

这是什么目的?如果我不这样做，我的代码会不会出错?还是它可以启用更多用例(即某种多态性)，因为人们可以覆盖这些布尔强制?

What is the purpose of this? Will my code be buggier if I don't do this? Or does it enable more use cases (i.e: some kind of polymorphism) since people can override these boolean coercions?

推荐答案

此最佳做法并非没有道理.

This best practice is not without reason.

在测试 if object:时，您基本上是在调用对象 __ bool __ 方法，该方法可以根据对象行为进行覆盖和实现.

When testing if object: you are basically calling the objects __bool__ method, which can be overridden and implemented according to object behavior.

例如，集合上的 __ bool __ 方法(Python 2中为 __ nonzero __ )将根据集合是否为空返回布尔值.

For example, the __bool__ method on collections (__nonzero__ in Python 2) will return a boolean value based on whether the collection is empty or not.

(参考: http://docs.python.org/reference/datamodel.html )

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