OR语句处理两个！=子句Python [英] OR statement handling two != clauses Python

问题描述

(使用Python 2.7)我理解这是很基本的，但是为什么下面的语句不能按原样工作:

(Using Python 2.7) I understand this is pretty elementary but why wouldn't the following statement work as written:

input = int(raw_input())
while input != 10 or input != 20:
    print 'Incorrect value, try again'
    bet = int(raw_input())

基本上，我只想接受10或20作为答案.现在，无论输入"，即使是10或20，我都会得到错误值".这些条款会自相矛盾吗?我认为只要其中一个子句是正确的，OR语句就会说确定".谢谢！

Basically I only want to accept 10 or 20 as an answer. Now, regardless of 'input', even 10, or 20, I get 'Incorrect value'. Are these clauses self conflicting? I thought that the OR statement would say OK as long as one of the clauses was correct. Thanks!

推荐答案

您需要 and :

You need and:

while input != 10 and input != 20:

仔细考虑:如果input是10，则第一个表达式是false，从而使Python评估第二个表达式input != 20. 10是不同于20的形式，因此该表达式的值为true.作为false or true == true，整个表达式为true.
与20相同.

Think it through: If the input is 10, then the first expression is false, causing Python to evaluate the second expression input != 20. 10 is different form 20, so this expressions evaluates to true. As false or true == true, the whole expression is true.
Same for 20.

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