TypeError: stat: path should be string, bytes, os.PathLike or integer, not NoneType

[luckyxianxian]

Hello,I use python3.6 to run the program.
But I had a problem like this,
if os.path.exists(result_dir) == False:
File "D:\Downloads\Software\python37\lib\genericpath.py", line 19, in exists
os.stat(path)
TypeError: stat: path should be string, bytes, os.PathLike or integer, not NoneType
If you have encountered this problem and it has been solved, please let me know, I would appreciate it.Thank you.