如何使嵌套的IF语句更整洁 [英] How to make nested IF statements neater

问题描述

这个问题可以用语言独立的方式提出，但我在python的上下文中提问，因为不同的语言会有不同的细微差别。

This question could be asked in a language independent way but I'm asking in the context of python since different languages will have different nuances.

我认识到这一点类似于这个问题，但我认为我的是不同之处在于我在询问将两个条件与& 放在同一if语句中的情况会产生错误。

I recognize that this is similar to this question but I think mine is different in that I'm asking about a case where putting the two conditions in the same if statement with & will generate an error.

假设我想看看 abc [x] 是否等于'fish'但是我要说我不确定 len（abc）是> =到x。我不能只有如果abc [x] =='fish'因为它可能是索引超出范围。因此我需要做

Let's say I want to see if abc[x] is equal to 'fish' but let's say I don't know for sure that len(abc) is >= to x. I can't just have if abc[x]=='fish' because it might be index out of range. As such I need to do

if len(abc)>x:
    if abc[x]=='fish':
        dostuff
    else:
        dootherstuff
else:
    dootherstuff

有没有更简洁的方法可以做到这一点，我没有两个其他语句最终做同样的 dootherstuff ？如果我想改变什么 dootherstuff 晚于我必须在两个地方改变它，但到那时我可能会忘记。当然我可以尝试评论代码以便稍后提醒自己或者使用 dootherstuff 一个函数，但这仍然是第二好的。很多时候，当我结束这个时， dootherstuff 只是一行代码，因此即使它解决了后续的变化，使它成为一个函数并不会感觉好多少场景。

Is there a cleaner way to do this where I don't have two else statements that end up doing the same dootherstuff? If I want to change what dootherstuff is later than I have to change it in both places but by then I might forget. Sure I could try to comment the code to remind myself later or make dootherstuff a function but that still seems second best. A lot of times when I wind up doing this the dootherstuff is just a one line of code so making it a function doesn't feel much better even though it addresses the subsequent change scenario.

推荐答案

当然，这是：

if len(abc) > x and abc[x] == 'fish':
    dostuff
else:
    dootherstuff

和短路，所以 abc [x] =='fish'只会如果 len（abc）>则进行评估x 是 True 。大多数语言都有类似的运算符（例如，C中的&& ）。

and short-circuits, so abc[x] == 'fish' will only be evaluated if len(abc) > x is True. Most languages have a similar operator (e.g. && in C).

& 用于按位和，并且不会短路，所以请勿使用那。

& is for bitwise "and," and doesn't short-circuit, so don't use that.

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