Can I use map to perform iterative update on a list?

Here’s part of the code I am working on. My goal is to start from the empty list D_E, then accumulate results of de into D_E, from the for loops.

D_E = []
for num_flip in range (0, N):
    probsu = []
    de = []
    for i in range (L):
        probsui = []
        for j in range (nuni):
            counts = results.get_counts((nuni*i)+j)
            prob = absorb_counts(counts)[num_flip]/sum(counts.values())
            probsui.append(prob)
            pz_bar = np.average(probsui)
        probsu.append(pz_bar)
        de.append(np.abs(5 - math.comb(N, num_flip)))
    spec = dict(zip(EW,probsu))
    # Here, I want to perform an iterative update of D_E
    D_E = list(map(add, D_E, de))

D_E = dict(zip(EW, [0.5*i for i in D_E]))
print(D_E)

I initialized D_E to be an empty list, and in my for loop for num_flip, I am trying to update D_E by adding de, another list. I am not appending de, but want to add all its elements to D_E. Since I am repeating this procedure, I wonder if I could use map in the for loop, and update D_E. However, currently my final result of D_E is just {}. I don’t know where I am doing wrong.

I tried a simpler example: D_E = dict(zip([1,2,3], [0.5*i for i in [1,2,3]])) and that worked well, I wonder how can I use map in the for loop in my case?

>Solution :

Based on the discussion on the comments, you need to initialise D_E before summing the new values. The following code should work (I left the rest of the code as is, even the parts that are never used, such as spec).

D_E = [0 for _ in range(L)]
for num_flip in range (0, N): # Note: range normally starts from 0, so range(N) is enough
    probsu = []
    de = []
    for i in range (L):
        probsui = []
        for j in range (nuni):
            counts = results.get_counts((nuni*i)+j)
            prob = absorb_counts(counts)[num_flip]/sum(counts.values())
            probsui.append(prob)
            pz_bar = np.average(probsui)
        probsu.append(pz_bar)   # Note: this is never used
        de.append(np.abs(5 - math.comb(N, num_flip)))
    spec = dict(zip(EW,probsu))   # Note: this is never used
    # Here, I want to perform an iterative update of D_E
    D_E = list(map(add, D_E, de))

D_E = dict(zip(EW, [0.5*i for i in D_E]))
print(D_E)