Question

请考虑以下简化模式：

export class ConteudoprodutoPage {

produto: Produto;

constructor(private payPal: PayPal, public navCtrl: NavController, public 
navParams: NavParams) {
this.produto = navParams.get("valor");
}

以及它的重构版本：

def nested_ifs():
    if some_condition is True:
        # possibly do something
        if another_condition is True:
            if another is True:
                return do_this()
    # or do something else
    return None

从可读性的角度来看，我个人更喜欢def flat_ifs(): if some_condition is not True: # or do something else return None # possibly do something if another_condition is not True: return None if another is not True: return None return do_this()的处理方式，但是性能上有区别吗？

Answer 1

令人惊讶的是，似乎嵌套循环实际上稍微快一点：

import datetime

def nested_ifs(x):
    if True:
        if True:
            if True:
                return 10*x
    return None

def flat_ifs(x):
    if not True:
        return None
    if not True:
        return None
    if not True:
        return None
    return 10*x


nr = 100000000

begin = datetime.datetime.now()
for i in range(nr):
    nested_ifs(i)

print("nested", datetime.datetime.now() - begin)

begin2 = datetime.datetime.now()
for i in range(nr):
    flat_ifs(i)

print("flat", datetime.datetime.now() - begin2)

给予我们

nested 0:00:14.960115
flat 0:00:16.157715

即使其中一个条件失败，也是如此。

如果有人能评论为什么嵌套方式要快一点的话，我将不胜感激

嵌套if语句与多个flat if not语句之间的性能

1 个答案: