Please see what's wrong with my Python Code-CodePudding

Why is this code not working? I keep getting "Invalid input" after every integer input, even if they are being considered as integers in the final maximum-minimum part of the code. Also the minimum keeps coming as "None". Please exlain it simply, im new to coding. Thank you.

largest = None
smallest = None

while True:
    num = input("Enter a number: ")
    if num == "done":
        break
    
    try: 
        num = int(num)
        if largest is None or largest < num:
            largest=num
        elif smallest > num or smallest is None:
            smalllest = num

    except:
        print("Invalid input")
        continue     

print("Maximum is", largest)
print("Minimun is", smallest)

I was expecting to see this output: "Invalid input" only for string text inputs, and the minimum code to work

CodePudding user response：

In the below, you have a typo. smalllest should be smallest.

       elif smallest > num or smallest is None:
           smalllest = num

Correcting that we note that "Invalid input" is only printed when you input a smaller number that the largest:

Enter a number: 56
Enter a number: 78
Enter a number: 89
Enter a number: 34
Invalid input
Enter a number: 45
Invalid input
Enter a number: 1
Invalid input
Enter a number: 67
Invalid input
Enter a number: 8999
Enter a number:

Your problem arises from the below. Because of the order of these conditions, smallest can be compared to num even if smallest is None.

elif smallest > num or smallest is None:

Which we can see generates an error:

>>> None > 56
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '>' not supported between instances of 'NoneType' and 'int'

Changing this to the following resolves the issue.

elif smallest is None or smallest > num:

Please also be aware that catching every possible exception with except: is a bad idea. Be more specific about which exceptions you're handling. As well, the continue is unnecessary. Having handled the exception, the loop will continue anyway.

largest = None
smallest = None

while True:
    num = input("Enter a number: ")
    if num == "done":
        break
    try: 
        num = int(num)
        if largest is None or largest < num:
            largest = num
        elif smallest is None or smallest > num:
            smallest = num
    except ValueError:
        print("Invalid input")

CodePudding user response：

One easy way to debug this is to catch and print your error. You may do so with

...
try:
    ...
except Exception as e:
    print(f"Exception {e}")
...

When you do this, you will see that when you enter a lower number than the max,

Exception '>' not supported between instances of 'NoneType' and 'int'

is printed.

This is due to smallest being None. I will leave fixing it as an exercise :)

CodePudding user response：

You have typo of smalllest->smallest that's why there is no change in the smallest variable

you can initialize largest and smallest as -infinity ,infinity respectively and than you can check for largest and smallest see the below code.

Code:

largest = -float('inf')  #Initialize to -inf
smallest = float('inf')  #Initialize to  inf

while True:
    num = input("Enter a number: ")
    if num == "done":
        break
    
    try: 
        num=int(num)
        if largest<num:  #check conditions.
            largest=num
        if smallest>num:
            smallest=num

    except:
        print("Invalid input")
        continue     

print("Maximum is", largest)
print("Minimun is", smallest)

Output:

Enter a number: 58
Enter a number: 78
Enter a number: 32
Enter a number: 16
Enter a number: 24
Enter a number: 99
Enter a number: done
Maximum is 99
Minimun is 16