import os

path = r'/Users/authurchen/PycharmProjects/Demo'

# print(os.listdir(path))

ls = os.listdir(path)
files = []

def get_all_file(dir_path):
    global files
    for filepath in os.listdir(dir_path):
        tmp_path = os.path.join(dir_path,filepath)
        if os.path.isdir(tmp_path):
            get_all_file(tmp_path)
        else:
            files.append(tmp_path)
    return files

def calc_files_size(files_path):
    files_size = 0
    for f in files_path:
        files_size += os.path.getsize(f)
    return files_size

files = get_all_file(path)
print(calc_files_size(files))