重复输入

Question

我想这样编程，因此在输入num1，num2和操作时，如果用户未以适当的类型提供输入，则会再次询问用户输入。

operation=(input('1.add\n2.subtract\n3.multiply\n4.divide'))
num1 =int(input("Enter first number: "))
num2 = int(input("Enter second number: "))

if operation == "add" or operation == '1' :
   print(num1,"+",num2,"=", (num1+num2))
elif operation =="subtract" or operation == '2':
   print(num1,"-",num2,"=", (num1-num2))
elif operation =="multiply" or operation == '3':
   print(num1,"*",num2,"=", (num1*num2))
elif operation =="divide" or operation == '4':
   print(num1,"/",num2,"=", (num1/num2))

Answer 1

您可以使用in关键字。

例如：

>>> "1" in ["1","add"]
True
>>> "add" in ["1","add"]
True

修改代码，例如：

 operation=(input('1.add\n2.subtract\n3.multiply\n4.divide'))

    num1 = int(input("Enter first number: "))
    num2 = int(input("Enter second number: "))

    if operation in ["1","add"] :
       print(num1,"+",num2,"=", (num1+num2))
    elif operationi in ["2", "subtract"]:
       print(num1,"-",num2,"=", (num1-num2))
    elif operation in ["3", "multiply"]:
       print(num1,"*",num2,"=", (num1*num2))
    elif operation in ["4", "divide"]:
       print(num1,"/",num2,"=", (num1/num2))
    else:
        print("Invalid Input")

Answer 2

尝试一下

 operation=(input('1.add\n2.subtract\n3.multiply\n4.divide'))

    num1 = int(input("Enter first number: "))
    num2 = int(input("Enter second number: "))

    if operation == "1" or operation == "add" :
       print(num1,"+",num2,"=", (num1+num2))
    elif operation == "2" or operation == "subtract":
       print(num1,"-",num2,"=", (num1-num2))
    elif operation == "3" or operation == "multiply":
       print(num1,"*",num2,"=", (num1*num2))
    elif operation == "4" or operation == "divide":
       print(num1,"/",num2,"=", (num1/num2))
    else:
        print("Invalid Input")

说明：

在您的代码中， IF 将检查条件1或条件2为真还是假

if operation == "1" or operation == "add" 

在这里

条件1： operation == "1"

条件2： operation == "add"

if operation == "1" or operation == "add" 

在这里

condition-1： operation == "1"

条件2： "add" # Always True as string contains elements.

Answer 3

此代码有效，因为在Python中，值是真实的和虚假的。但是，多条件if子句的语法错误。应该是if a == something and b == anotherthing。

因此它将如下。

if operation == "1" or operation == "add" :
    print(num1,"+",num2,"=", (num1+num2))