Python issues with return statement

You are discarding the return value for the recursive call:

def isPrime(i,n):
    if ((n % i == 0) and (i <= math.sqrt(n))):
        return False
    if (i >= math.sqrt(n)):
        print ("is Prime: ",n)
        return True
    else:
        # No return here
        isPrime(i+1,n)

You want to propagate the value of the recursive call too, include a return statement:

else:
    return isPrime(i+1,n)

Now your code prints:

>>> isPrime(2,7)
is Prime:  7
True