编写If语句的两种不同方式.为什么第二个不起作用? [英] Two different ways of writing the If Statement. Why the second is not working?

问题描述

我目前正在学习"if语句"，并做了一个权重换算练习.

I'm currently learning about "if statements" and I did a weight converter as an exercise.

这是正确的方法，没关系，我理解:

This is the correct way and it's fine, I understand it:

weight=int(input("your weight: "))
choice=input("lbs[L] or kilos[K] ? ")

if choice.upper() == "L":
    print(f"your weight is {weight * 0.45} kilograms")
elif choice.upper() == "K":
    print(f"your weight is {weight / 0.45} pounds ")
else:
    print("choose lbs or kilograms")

但是我以自己的方式完成了此操作，但它不起作用，但是为什么呢?

But I did this in my way and it is not working, but why?:

weight=int(input("your weight: "))
choice=input("lbs[L] or kilos[K] ? ")

if choice == "L" or "l":
    print(f"your weight is {weight * 0.45} kilograms")
elif choice == "K" or "k":
    print(f"your weight is {weight / 0.45} pounds ")
else:
    print("choose lbs or kilograms")

如果有人可以告诉我为什么第二个代码不起作用? 我会很高兴.

Please if someone could tell me why is the second code not working ? I will be glad.

推荐答案

if choice == "L" or "l":

与说if (choice == "L") or ("l"):

其中第一组括号是您期望的，第二组检查"l"是True，其为

where the first set of brackets is what you expect, and the second checks that the "l" is True, which, as a non-empty string, it always is.

您需要明确地说:

if choice == "L" or choice == "l":

，或者如果您不想使用upper()或lower():

or alternatively if you don't want to use upper() or lower():

if choice in ["L", "l"]:

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