Calculate the size of the folder using Python

CalculateSizeFolder.py

import os

res = []

def readFolder(file):
    if os.path.isfile(file):
        res.append(os.path.getsize(file))
    else:
        arr = os.listdir(file)
        for element in arr:
            child = file + "\\" + element

            if os.path.isfile(child):
                res.append(os.path.getsize(child))
            else:
                readFolder(child)
    return sum(res)


# path = 'D:\English\English_Collocations_in_Use_Advanced.pdf'
# path = 'D:\English\CDIeltsband5.5-6.5.rar'
path = 'D:\English'
# print(readFolder(path))

arr = readFolder(path)
print(arr)

# print(os.path.isfile("D:\English\TOEIC\900A\Test10 - Tu luyen TOEIC 900.mp3"))