如何Python的条件运算解决方法的工作？

本文介绍了如何Python的条件运算解决方法的工作？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

从我读过，我发现一个内置的三元运算符不存在（我会很乐意多了解一下。）

From what I have read, I found that a built-in ternary operator does not exist (I will be happy to know more about it.).

我发现下面的code作为替代：

I found the following code as a substitute:

def val():
    var = float(raw_input("Age:"))
    status = ("Working","Retired")[var>65]
    print "You should be:",status

我不明白这是如何code工作;任何人都可以解释我是如何实际上是code为工作？我也有兴趣知道为什么三元运算符不存在;这个任何参考或链接将矿石有用。

I couldn't understand how this code works; can anyone explain me how actually the code is working? I am also interested to know why the ternary operator doesn't exist; any references or links about this will be ore useful.

我在Windows Vista上运行的Python 2.6.4。

I'm running Python 2.6.4 on Windows Vista.

推荐答案

Python有一个结构，它是有点像在C三元运算等。它的工作原理是这样的：

Python has a construct that is sort of like the ternary operator in C, et al. It works something like this:

my_var = "Retired" if age > 65 else "Working"

和相当于这个C code：

and is equivalent to this C code:

my_var = age > 65 ? "Retired" : "Working";

至于如何code您发布的作品，让我们通过它一步：

As for how the code you posted works, let's step through it:

("Working","Retired")

创建了一个2元组（不可变列表）与索引0元素工作和退役索引1。

creates a 2-tuple (an immutable list) with the element "Working" at index 0, and "Retired" at index 1.

var>65

如果无功大于65，假如果不返回True。当应用于一个指数，它被转换成1（真）或0（假）。因此，该布尔值提供一个索引在同一行中创建的元组

returns True if var is greater than 65, False if not. When applied to an index, it is converted into 1 (True) or 0 (False). Thus, this boolean value provides an index into the tuple created on the same line.

为什么没有Python中一直有一个三元运算符？简单的答案是，吉多·范罗苏姆，巨蟒的作者，不喜欢/不想要它，显然认为这是谁的看到大量嵌套不必要的结构，可能会导致混乱code（以及任何三元运营商在C能大概一致）。但对于Python 2.5，他心软了，并添加上面看到的语法。

Why hasn't Python always had a ternary operator? The simple answer is that Guido van Rossum, the author of Python, didn't like/didn't want it, apparently believing that it was an unnecessary construct that could lead to confusing code (and anyone who's seen massively-nested ternary operators in C can probably agree). But for Python 2.5, he relented and added the grammar seen above.

这篇关于如何Python的条件运算解决方法的工作？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！

python