Stop while loop if user inputs correct operator

Question

I just started learning Python yesterday and one of the programs I'm trying to write is a calculator. This segment of code is where I'm having problems. The while loop is supposed to stop when the user inputs any of the math operators but it still asks for input even when the user enters one the correct characters.

What do I need to do to fix this.

    op = None                                 
    while (op != "-" or op != "+" or op != "*" or op != "/"):
        op = input("Enter operator (-, +, *, /):  ")
    print(op)

Christian Trujillo · Accepted Answer · 2022-08-06 00:01:16Z

3

  op = None                                 
while op not in ["-","+","*","/"]:
    op = input("Enter operator (-, +, *, /):  ")
print(op)

or

op = None                                 
while (op != "-" and op != "+" and op != "*" and op != "/"):
    op = input("Enter operator (-, +, *, /):  ")
print(op)

your code isnt working because while "op" might be equal to one of your options, its not equal to all the others, and therefore continues the loop

answered Aug 6, 2022 at 0:01

Christian Trujillo

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6 Comments

BeRT2me Over a year ago

The not in technique is exactly what I was going to post, but I'd use a tuple rather than a list as tuples are faster.

BeRT2me Over a year ago

For some reasons why, you can see here

Christian Trujillo Over a year ago

informative, thankyou, so tuples are built about 3x faster than lists, and tuples made of literals (rather than variables) are built about 6x faster

BeRT2me Over a year ago

Yep, lists are used for their mutability, but if it's not going to be changed, a tuple is better~

mipadi Over a year ago

You can also use a string: while op not in "-+*/":

|

Ariel Kwiatkowski · Accepted Answer · 2022-08-05 23:56:50Z

2

You don't want or between the conditions, you want and.

answered Aug 5, 2022 at 23:56

Ariel Kwiatkowski

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Comments

kumarhimself · Accepted Answer · 2022-08-06 00:02:14Z

1

The other answers are great, but I wanted to show you a piece of code called the break statement. Here is a more detailed explanation, but basically, a break statement breaks out of an iterative loop like a while loop. Here is how your code would look if you used a break statement:

op = None                                 
while (op != "-" or op != "+" or op != "*" or op != "/"):
  op = input("Enter operator (-, +, *, /):  ")

  if op == "-" or op == "+" or op == "*" or op == "/":
    break

print(op)

answered Aug 6, 2022 at 0:02

kumarhimself

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1 Comment

BeRT2me Over a year ago

This would be better shown with while True: imo~

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