np.gentext loop and fill empty array in python

Question

I have 50 different folders (from 0 to 50) with the data I want to plot named as data_A, data_B, data_C, data_D. How do I iterate through the 50 folders, collect the data, apply a numerical operation and print the output (V) to a list? The final goal would be to make a boxplot of (V) for each folder.

Hope that this attempt of code helps in understanding my aim:

directory='/path_to_data/'

folders = [0..50]

for i in (len(folders)):
        A = (np.genfromtxt(directory/[i]/'data_A.dat')
        B = (np.genfromtxt(directory/[i]/'data_B.dat')
        C = (np.genfromtxt(directory/[i]/'data_C.dat') 
        D = (np.genfromtxt(directory/[i]/'data_D.dat') 

        V = (A+B+C+D)/4 #make and average of the data
        
    DATA=[V,..]
    NAMES=[folder$i,.. ]
done

Thanks!