为什么函数对象在python中评估为True? [英] Why do function objects evaluate to True in python?

问题描述

在python中进行如下构造是有效的:

In python it is valid to make a construction like:

def a(): 
    return 0

if a: 
    print "Function object was considered True"
else:  
    print "Function object was considered False"

我想问一个函数指针被评估为True的逻辑是什么.

I wish to ask what is the logic that a function pointer is evaluated to True.

为什么在语言中插入了这种构造?

Why was this kind of construction inserted in the language?

推荐答案

许多事情在Python中的评价为True.从关于布尔运算符的文档:

A lot of things evaluate to True in Python. From the documentation on Boolean operators:

在布尔运算的上下文中，以及当控制流语句使用表达式时，以下值将解释为false:False，None，所有类型的数字零以及空字符串和容器(包括字符串，元组，列表，字典，集合和Frozensets).所有其他值都解释为true.

In the context of Boolean operations, and also when expressions are used by control flow statements, the following values are interpreted as false: False, None, numeric zero of all types, and empty strings and containers (including strings, tuples, lists, dictionaries, sets and frozensets). All other values are interpreted as true.

Python中的函数与许多事物一样，都是对象，并且不是空的.因此，在布尔值上下文中，它们的评估结果为True.

Functions in Python, like so many things, are objects, and not empty. Thus, in a boolean context, they evaluate to True.

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