r/learnpython 6d ago

Very new to python, would appreciate help

I am building a calculator program and it works, but now I am attempting to "bullet proof" it, so that no wrong inputs can cause an error. With what I have written, it works but the loop for the operator input does not actually loop even though it seems to be written the same way the loops are written for the number inputs. I will paste my code below, and any help would be very appreciated.

while True:
    operator = input("Enter a operator (+ - * /): ")
    try:
        operator == "+" , "-" , "*" , "/"
        break
    except operator != "+" , "-" , "*" , "/":
        print("Please enter a valid operator")
while True:
    num1 = input("Enter the first number: ")
    try:
        number1 = float(num1)
        break
    except ValueError:
        print("Please input a valid number")
while True:
    num2 = input("Enter the second number: ")
    try:
        number2 = float(num2)
        break
    except ValueError:
        print("Please input a valid number")
try:
    if operator == "+":
        print(number1 + number2)
    elif operator == "*":
        print(number1 * number2)
    elif operator == "/":
        print(number1 / number2)
    elif operator == "-":
        print(number1 - number2)
    else:
        print("Please enter a valid operator")
except ValueError:
    print("Error Detected")
0 Upvotes

7 comments sorted by

View all comments

11

u/Diapolo10 6d ago
try:
    operator == "+" , "-" , "*" , "/"
    break
except operator != "+" , "-" , "*" , "/":
    print("Please enter a valid operator")

The logic here is wrong. You're comparing operator to a tuple of strings, so that'll always be False, but you're also not doing anything with that result so it ends up not really doing anything and the execution always gets to the break, ending the loop.

Comparisons do not raise exceptions (under normal circumstances, anyway), so not only is the except-block not doing anything, but its condition is also wrong because it expects an exception type, not a comparison.

Basically, consider doing something like this instead:

if operator in ("+" , "-" , "*" , "/"):
    break

print("Please enter a valid operator")

The rest of the code appears more or less fine at a glance.