如何用多行写python lambda? [英] How to write python lambda with multiple lines?

问题描述

在python中，如何编写包含多行代码的lambda函数.我尝试过

In python, how can you write a lambda function taking multiple lines. I tried

d = lambda x: if x:
                 return 1
              else 
                 return 2

但是我遇到了错误...

but I am getting errors...

推荐答案

请改用def.

def d(x):
    if x:
        return 1
    else:
        return 2

所有python函数都是一阶对象(它们可以作为参数传递)，lambda只是一种简短的简便方法.通常，如果普通函数定义超出了简单代码的一行，则最好使用普通函数定义.

All python functions are first order objects (they can be passed as arguments), lambda is just a convenient way to make short ones. In general, you are better off using a normal function definition if it becomes anything beyond one line of simple code.

实际上，即使您将其分配给一个名称，我也总是会在lambda上使用def.在定义短的key函数(例如与sorted()一起使用)时，lambda实际上只是一个好主意，因为它们可以内联放置在函数调用中.

Even then, in fact, if you are assigning it to a name, I would always use def over lambda. lambda is really only a good idea when defining short key functions, for use with sorted(), for example, as they can be placed inline into the function call.

请注意，在您的情况下，三元运算符可以完成此任务(lambda x: 1 if x else 2)，但是我认为这是一种简化的情况.

Note that, in your case, a ternary operator would do the job (lambda x: 1 if x else 2), but I'm presuming this is a simplified case.

(作为代码笔记，这也可以用lambda x: bool(x)+1更少的代码来完成-当然，这是非常难以理解的，也是一个坏主意.)

(As a code golf note, this could also be done in less code as lambda x: bool(x)+1 - of course, that's highly unreadable and a bad idea.)

这篇关于如何用多行写python lambda?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！