It would make sense to me to upgrade this particular error message toTraceback (most recent call last):
File "foo.py", line 2, in <module>
l[10]=14
IndexError: list assignment index out of range
A better message might be:
You tried to use l[10] when l is only 4 elements long. You can add items to l using l.append(value), or check your index value to make sure that's really the position you wanted to access.