Python list all files in dir recursivelly

import os

idx=0
def list_dir_files(dir_name):
    global idx
    if os.path.exists(dir_name):
        all_items=os.listdir(dir_name)
        for item in all_items:
            full_path=os.path.join(dir_name,item)
            if os.path.isfile(full_path):
                idx+=1
                print('file:',idx,os.path.join(dir_name,item))
            elif os.path.isdir(full_path): 
                print("dir:",full_path)
                list_dir_files(full_path)

if __name__=="__main__":
    dir=r"D:\C"
    list_dir_files(dir)