How to calculate the integral from the square of defined function in Python?

I have a problem with calculating the integral in Python.

So, I have defined function:

def function_f(x):
    if x>=0 and x<=1: 
        return ((1/3)**x)
    else:
        return 0

I know to calculate the simple one (without square), with this code:

from scipy import integrate
integrate.quad((function_f), 0, 1)

But the problem is that I need to calculate the integral from the square of this function, so I need integral from (function_f)^2.

I hope that you have some advices how I can do that.

Solution

I'm not used to scipy.integrate, but based on your explanations you should be able to do :

integrate.quad(lambda x:function_f(x)**2, 0, 1)