foldersizes.py

import os
import numpy as np


def get_size(start_path = '.'):
    total_size = 0
    for dirpath, dirnames, filenames in os.walk(start_path):
        for f in filenames:
            fp = os.path.join(dirpath, f)
            total_size += os.path.getsize(fp)
    return total_size


folder_sizes = []

for f in os.listdir('.'):
    if os.path.isdir(f):
        folder_sizes.append(get_size(f))

avg_size = np.average(folder_sizes)
med_size = np.median(folder_sizes)

print 'Average size: {} bytes / {:.1f} MB / {:.1f} GB'.format(int(avg_size), avg_size/(1024**2), avg_size/(1024**3))
print 'Median size: {} bytes / {:.1f} MB / {:.1f} GB'.format(int(med_size), med_size/(1024**2), med_size/(1024**3))