Multiplicate several numbers

[nilamo]

Start with func = 1 before the loop, and then each time you calculate the new value, do func *= calculated_value to multiply it into the rolling total.

Edit:
Or, if you write your function as a function, you can use map/reduce to do the same thing much cleaner:

>>> import functools
>>> import operator
>>> def func(x):
...   return 1 + (1/(x**2))
...
>>> functools.reduce(operator.mul, map(func, range(1, 19)))
3.482783207792457