Reason for Key Error being returned?

Question

I'm using this Scrabble code to translate letters into numbers, but whenever I try to run it, it returns a Key Error: ' ', and I don't know why this happens or how to fix it.

score = {"a": 1, "c": 3, "b": 3, "e": 1, "d": 2, "g": 2, 
         "f": 4, "i": 1, "h": 4, "k": 5, "j": 8, "m": 3, 
         "l": 1, "o": 1, "n": 1, "q": 10, "p": 3, "s": 1, 
         "r": 1, "u": 1, "t": 1, "w": 4, "v": 4, "y": 4, 
         "x": 8, "z": 10}
def tracker():
    word = input("Please enter a word.")
    total = 0
    for i in word:
        total = total + score[i.lower( )]
    print(total)
    return total
def main():
    tracker()
main()

Returns the error:

Please enter a word. Yellow
Traceback (most recent call last):
  File "H:\Scrabble.py", line 15, in <module>
    main()
  File "H:\Scrabble.py", line 14, in main
    tracker()
  File "H:\Scrabble.py", line 10, in tracker
    total = total + score[i.lower( )]
KeyError: ' '

Answer 1

Your input probably has a space that is not in the score dictionary. try:

above score

unknown_char=0
#Whatever the unknown char data should be

in tracker()

for i in word:
    try:
        total += score[i.lower()]
    except:
        total += unknown_char

Answer 2

In any program that requires user's input, you need to manage input errors .

I suggest using .strip() method on the word you will iterate on. It'll get rid of the spaces. Also, you might want to check if the character is in your dictionnary, I believe you should do as such :

if i not in word : raise ValueError("Your error message.")

Also, when iterating through your dict, you should use .items() (python 3.x) or .iteritems() (python 2.7) if you need the key and the value, as such :

for key, value in your_dict.iteritems():