[Tutor] Help with Recurring Function

[Sanhita Mallick]

Hi.

I am struggling with a simple recurring function, but
can't understand why this is happening. Please help.

Here is the script. T(i) are trees (as in graphs).
The program operates great, until the step where
norm_ted is calculated. Mysteriously norm_ted becomes
0, even though "mag" value is calculated correctly.
Also, strangely, sum_norm_ted also becomes zero. 

What am I missing?

Thanks.
-Sanhita

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
T = [F1, F2, F3]
k = len(T)
mean_ted = {}
for i in range(k):    
    sum_norm_ted = 0.0
    mag = 0.0
    norm_ted = 0.0
    for j in range(k):
        if (i != j):
            ted= alg.ted(T[i], T[j])
            print 'TED ' + str(i) + str(j) + ' is ' +
str(ted)
            mag = 2 * (T[i].n + T[j].n) - 1
            print 'MAG ' + str(i) + str(j) + ' is ' +
str (mag) + ' and ' + str ( 2 * ted )
            norm_ted = (2 * ted) / mag 
            print 'norm_ted ' + str(i) + str(j) + ' is
' + str (norm_ted)
            sum_norm_ted = sum_norm_ted + norm_ted
            print 'sum_norm_ted ' + str(i) + str(j) +
' is ' + str (sum_norm_ted)