单行for循环作为函数参数 [英] One-line for loop as a function argument

问题描述

def strange_syntax(stuff):
    return ".".join(item for item in stuff)

该代码如何(以及为什么)起作用?发生什么事了?通常我不能使用这种语法.另外，如果它不在某些 function 中作为参数，则该语法也不存在.

How (and why) works this code? What happens here? Normally I can't use this syntax. Also, this syntax doesn't exist if it's not inside some function as an argument.

我知道，我可以这样做:

I know, I could do the same with:

def normal_syntax(stuff):
    return ".".join(stuff)

推荐答案

在函数调用中使用时，语法:

When used in a function call, the syntax:

f(a for a in b)

隐式编译为生成器，意思是

implicitly is compiled as a generator, meaning

f((a for a in b))

这只是语法糖，使程序看起来更好.直接在控制台中编写并没有多大意义

This is just syntactic sugar, to make the program look nicer. It doesn't make much sense to write directly in the console

>>>a for a in b

因为尚不清楚是要创建生成器还是执行常规循环.在这种情况下，您必须使用外部().

because it's unclear if you want to create a generator, or perform a regular loop. In this case you must use the outer ().

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