Python: ValueError '3' is not in list

Question

I'm new to programming and I don't understand this error. I have a program that is supposed to tell you the numerical position of an alphabet from a given letter input. If the input is not an alphabet it should return 'does not belong to the alphabet'. However I'm getting a ValueError when giving a number input.

The code I'm working on:

alphabets = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','å','ä','ö']

myAlphabet = input("Enter the letter you are looking for in the alphabet:")
Number0OfA = alphabets.index(myAlphabet)

for myAlphabet in alphabets:
    if myAlphabet in alphabets:
        print(myAlphabet ,'is the', Number0OfA, '. alphabet')
        break
    else:
        print(myAlphabet , 'does not belong to the alphabet')

The error:

Exception has occurred: ValueError
'3' is not in list
  File "C:\Users\me\pycode\main.py", line 4, in <module>
    Number0OfA = alphabets.index(myAlphabet)

Any help would be great.

Answer 1

The reason for failure is, your list does not contain 3, and hence when index() tries to get the location of 3 it does not find it and hence says ValueError.
There's actually no need of a for loop. It can simply be done using in as below:

alphabets = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','å','ä','ö']

myAlphabet = input("Enter the letter you are looking for in the alphabet:")
if myAlphabet in alphabets:
    print(myAlphabet ,'is the', alphabets.index(myAlphabet), '. alphabet')
else:
    print(myAlphabet , 'does not belong to the alphabet')

However if you still want to use a for loop, below is the way:

alphabets = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','å','ä','ö']

myAlphabet = input("Enter the letter you are looking for in the alphabet:")
if myAlphabet not in alphabets:
    print (myAlphabet , 'does not belong to the alphabet')
else:
    for index in range(len(alphabets)): 
        if myAlphabet == alphabets[index]:
            print(myAlphabet ,'is the', index, '. alphabet')
            break
        

Output:

Enter the letter you are looking for in the alphabet:z
z is the 25 . alphabet