Question

我必须在python 3上做这个计算器，该计算器必须在用户输入exit之前循环执行。此外，在用户键入无效字符（例如要求输入操作员的字母或数字）之前，请进行编程。

我必须使用while，if...。但是，我不能使用import 。

while True:

    operator = input("Give me an operator or \"exit\" to stop : ")

    if operator == "exit":
        break
    if operator != "+" or "-" or "*" or "/":

        print ("You must enter an operator")
        break
    no1 = input("Enter a number: ")
    no2 = input("Enter a number: ")
    if operator == "+":
        output = int(num1) + int(num2)
    elif operator == "-":
        output = int(num1) - int(num2)
    elif operator == "*":
        output = int(num1) * int(num2)
    else :
        output = int(num1) / int(num2)
    print("The result is " + str(result))
print("See you soon!")

我希望当我们输入除运算符之外的任何内容时，它实际上不会停止，我希望它循环回到：

operator = input("Give me an operator or \"exit\" to stop : ")

Answer 1

在此之下，您会找到可以正常工作的代码，但是让我们从一般规则入手。

请注意，在声明变量时，请在代码中的其他位置使用该变量。
在尝试编写脚本之前，测试代码的简单部分。您对测试操作员的条件完全被破坏了。

while True:

    operator = input("Give me an operator or \"exit\" to stop : ")

    if operator == "exit":
        break
    if operator not in [ "+", "-", "*" , "/"]: #<== here you condition is wrong ,do this instead

        print ("You must enter an operator")
        continue
    try:
        num1 = int(input("Enter a number: ")) #
        num2 = int(input("Enter a number: ")) # <== both of this variable are not use else where ,rename to be consitdnt with the rest of your code
    except ValueError:
        print("Please enter an integer") 
    if operator == "+":
        output = num1 + num2
    elif operator == "-":
        output = num1 - num2
    elif operator == "*":
        output = num1 * num2
    else :
        output = num1 / num2
    print("The result is " + str(output)) #<=== here also, results was not defined 
print("See you soon!")

Answer 2

放入通用的 else 语句，该语句将在下一次迭代中继续。

if condition1 :
  //logic
elif condition2 :
  //logic
else:
  continue

Answer 3

您的问题是您在做什么：
if operator != "+" or "-" or "*" or "/":
真正在做的是：
if operator != "+" or 45 or 42 or 47:（这些字符的ASCII表示形式）
这意味着无论如何条件都成立，因为or n的N不为0会随时通过。

您要：
if operator != "+" and operator != "-" and operator != "*" and operator != "/":
您需要一个AND门。

此外，我注意到您说的是no1 = input(...)，然后是int(num1)，而不是int(no1)。

要跳回输入，请使用continue
最终代码：

while True:

    operator = input("Give me an operator or \"exit\" to stop : ")
    if operator == "exit":
        break
    if operator not in [ "+", "-", "*" , "/"]: # credit to Florian Bernard for this line :)
        print ("You must enter an operator")
        continue

    num1 = input("Enter a number: ")
    num2 = input("Enter a number: ")
    if operator == "+":
        output = int(num1) + int(num2)
    elif operator == "-":
        output = int(num1) - int(num2)
    elif operator == "*":
        output = int(num1) * int(num2)
    else:
        output = int(num1) / int(num2)
    print("The result is " + str(output)) # this was previously str(result) but result is was not defined
print("See you soon!")

但是！如果您今天感觉很新，可以使用PEP 572中引入的{strong> walrus运算符，该语言可以从python 3.8

获得

while (operator := input("Give me an operator or \"exit\" to stop : ")) != "exit":
    if operator not in [ "+", "-", "*" , "/"]: # credit to Florian Bernard for this line :)
        print ("You must enter an operator")
        continue

    num1 = input("Enter a number: ")
    num2 = input("Enter a number: ")
    if operator == "+":
        output = int(num1) + int(num2)
    elif operator == "-":
        output = int(num1) - int(num2)
    elif operator == "*":
        output = int(num1) * int(num2)
    else:
        output = int(num1) / int(num2)
    print("The result is " + str(output))
print("See you soon!")

编辑：
编辑了最终代码以使用continue，以前的版本是。
还添加了python 3.8实现。

EDIT2：
只是纠正一些东西，使句子更真实。

计算器执行循环直到“退出”

3 个答案: