编写if语句的更短，更pythonic的方式

I have this

我有这个

bc = 'off'

if c.page == 'blog':
    bc = 'on'

print bc

Is there a more pythonic (and/or shorter) way of writing this in python?

在python中有更多的pythonic（和/或更短）的写法吗？

6 个解决方案

#1

Shortest one should be:

最短的应该是：

bc = 'on' if c.page=='blog' else 'off'

Generally this might look a bit confusing, so you should only use it when it is clear what it means. Don't use it for big boolean clauses, since it begins to look ugly fast.

通常这可能看起来有点令人困惑，所以你应该只在它清楚它意味着什么时使用它。不要将它用于大布尔子句，因为它开始看起来很难看。

#2

This is:

这是：

definitely shorter
绝对更短
arguably Pythonic (pre-Python 2.5, which introduced the controversial X if Z else Y syntax)
可以说是Pythonic（前Python 2.5，它引入了有争议的X，如果Z else Y语法）
questionably readable. With those caveats in mind, here it goes:

可疑的。考虑到这些警告，这里有：
```
bc = ("off","on")[c.page=="blog"]
```

EDIT: As per request, the generalized form is:

编辑：根据要求，通用表格是：

   result = (on_false, on_true)[condition]

Explanation: condition can be anything that evaluates to a Boolean. It is then treated as an integer since it is used to index the tuple: False == 0, True == 1, which then selects the right item from the tuple.

Explanation：condition可以是任何求值为Boolean的值。然后将其视为整数，因为它用于索引元组：False == 0，True == 1，然后从元组中选择正确的项。

#3

Well, not being a python guy please take this with a huge grain of salt, but having written (and, with more difficulty, read) a lot of clever code over the years, I find myself with a strong preference now for readable code. I got the gist of what your original code was doing even though I'm a nobody as a Python guy. To be sure, you could hide it and maybe impress a Python wonk or two, but why?

好吧，不要成为一个蟒蛇人，请带着巨大的盐，但多年来写了很多聪明的代码（并且，更难以阅读），我发现自己现在对可读代码有强烈的偏好。我得到了你的原始代码正在做的事情的要点，即使我是一个没有人作为Python人。可以肯定的是，你可以隐藏它并且可能会给Python一两个人留下深刻印象，但为什么呢？

#4

Or you could use an inline if statement:

或者您可以使用内联if语句：

>>> cpage = 'blog'
>>> bc = 'on' if cpage == 'blog' else 'off'
>>> bc
'on'
>>> cpage = 'asdf'
>>> bc = 'on' if cpage == 'blog' else 'off'
>>> bc
'off'

There's a bit of a writeup on that feature at this blog, and the relevant PEP is PEP308. The inline if statement was introduced in Python 2.5.

在这个博客上有关于该功能的一些文章，相关的PEP是PEP308。内联if语句是在Python 2.5中引入的。

This one might be a little less pythonic, but you can use and/or in this fashion:

这可能会少一些pythonic，但你可以使用和/或以这种方式：

>>> cpage = 'asdf'
>>> bc = (cpage == 'blog') and 'on' or 'off'
>>> bc
'off'
>>> cpage = 'blog'
>>> bc = (cpage == 'blog') and 'on' or 'off'
>>> bc
'on'

This one is used more often in lambda statements than on a line by itself, but the form

这个在lambda语句中经常使用，而不是在一行本身使用，而是在表单中使用

 A and B or C

is similar to

类似于

   if A:
       return B
   else:
       return C

I was going to write out a little bit longer explanation, but they covered it better at Dive into Python. They also noted a couple caveats that you probably need to know.

我打算写出更长一点的解释，但他们在Dive into Python中更好地介绍了它。他们还注意到您可能需要了解的一些警告。

#5

Another possibility is to use a dict if you can compute the values outside of the function that accesses them (i.e. the values are static, which also addresses the evaluation issue in scrible's answer's comments).

另一种可能性是使用dict，如果你可以计算访问它们的函数之外的值（即值是静态的，这也解决了scrible的答案评论中的评估问题）。

want_bc = {True: "on", False: "off"}
# ...
bc = want_bc[c.page == "blog"]

I prefer this and/or the tuple indexing solutions under the general rubric of preferring computation to testing.

我更喜欢这个和/或在优选计算到测试的一般标题下的元组索引解决方案。

#6

You can use,

您可以使用，

a = b if c else d

but if you are using a python version prior to 2.5,

但是如果你使用2.5之前的python版本，

bc = c.page == "blog" and "on" or "off"

can do the trick also.

也可以做到这一点。

#1