from os import listdir, rename
from os.path import isfile, isdir, join


def scroll_dir(dpath):
    children = [c for c in listdir(dpath)]
    for c in children:
        p = join(dpath, c)
        if isdir(p):
            scroll_dir(p)
        elif isfile(p):
            change_file_name(p)


def change_file_name(fpath):
    newname = str(fpath)\
        .replace(startpath, "")\
        .lstrip("/")\
        .replace("/", "__")
    newname = join(startpath, newname)

    rename(fpath, newname)
    print(f'{fpath} -> {newname}')


if __name__ == "__main__":
    print("/base/dir/subdir/file.mp4 -> /base/dir__subdir__file.mp4")
    startpath = input("base dir path: ")
    scroll_dir(startpath)