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避免在python中嵌套if-else语句阶梯

conditional-statements nested if-statement python

Bill · 技术社区 · 6 年前

当你不知道如何准确地描述这个问题时,很难找到答案…

处理一组相当深(但固定)的嵌套测试,最惯用的方法是什么?这些测试希望按顺序运行,但在第一组测试成功后立即终止?

而不是以下内容

选项1: (导致压痕过多)

def make_decision():

    results = ... some code or function that returns a list or None
    if results:
        decision = random.choice(results)
    else:
        results = ... other code or function
        if results:
            decision = random.choice(results)
        else:
            results = ... other code or function
            if results:
                decision = random.choice(results)
            else:
                results = ... other code or function
                if results:
                    decision = random.choice(results)

      ...etc.

                                else:
                                    decision = None

    print(decision)

    return decision

选项2

另一种选择是尽早从函数返回,但我不确定分散有这么多返回是一种好的做法,在这种情况下,我宁愿在最后做一件事(例如 print(decision) )返回前:

def make_decision():

    results = ... some code or function that returns a list or None
    if results:
        return random.choice(results)

    results = ... other code or function
    if results:
        return random.choice(results)

    results = ... other code or function
    if results:
        return random.choice(results)

    ...etc.

    else:
        decision = None

    return decision

选项3

最后,我可以使每个测试成为一个单独的函数 as described here 并且迭代地调用它们,前提是每个测试函数都有相同的参数集。

def test1(args):
    ...

def test2(args):
    ...

def test3(args):
    ...

def make_decision():

    decision = None
    for test in [test1, test2, test3, ...]:
        results = test(args)
        if results:
            decision = random.choice(results)
            break

    print(decision)

    return decision

这看起来是最好的,但我没有计划为每个测试都创建一个函数,有些测试可以用相同的函数完成,但是使用不同的参数,有些只是一行代码,而另一些是多行代码。那么,在开始循环之前,我需要构建一个函数和参数列表吗?或者列出 partial 功能?

欢迎提出更好的建议(在我继续执行上述选项3之前)

更新2018-07-21:

未来的潜在选择

我不知道我在和这个问题搏斗, PEP 572 得到了批准(范罗森因此辞职)。如果实施了该政治公众人物计划,我认为还可以采用以下解决方案:

def make_decision():

    if (results := ... some code or function) is not None:
        decision = random.choice(results)
    elif (results := ... some code or function) is not None:
        decision = random.choice(results)

    ...etc.

    else:
        decision = None

    return decision

2 回复 | 直到 6 年前

codejockie 6 年前

return True

elif results:

if results:
        # some code
    else:
        if results:
               # some code

results if if results == something

-2

Bill 6 年前

def make_decision():

    results = ... some code or function that returns a list or None

    if results is None:
        results = ... other code or function

    if results is None:
        results = ... other code or function

    ...etc.

    if results is None:
        decision = None
    else:
        decision = random.choice(results)
    print(decision)

    return decision