if l[k] is 10:
score+=10+l[k+1]+l[k+2];
k=k+1;
elif l[k]+l[k+1] is 10:
score+=10+l[k+2];
k=k+2;
That's what you posted. Identation is wrong here.
You can find that information in the forum. input() is equivalent to eval(raw_input()) and eval() cannot handle "\r" correctly. As some of the datasets have those EOLs and others have not, you will sometimes get AC using input() and sometimes you won't.
They affect the elegance of your code. They are ugly and needless.