Question

in the following program I got the index out of range error:

def evaluate(x, y):
    result = 0
    for i in x:
        result += (x[i])*(y**i)
    return result

Answer 1

You are already looping over all values of x, no need to then index them again:

def evaluate(x, y):
    result = 0
    for i in x:
        result += i * (y**i)
    return result

Compare the following two:

>>> x = [3, 2]
>>> for i in x:
...     print i
...
3
2
>>> for i in x:
...     print x[i]
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
IndexError: list index out of range

If you expected i to be an index into x, use enumerate() to get that index:

def evaluate(x, y):
    result = 0
    for i, value in enumerate(x):
        result += value * (y**i)
    return result