這是我的項目結構。[~/Sandbox/pystructure]:$ tree.├── pystructure│   ├── __init__.py│   ├── pystructure.py│   └── utils│       ├── eggs│       │   ├── base.py│       │   └── __init__.py│       ├── __init__.py│       └── spam.py├── README.md└── requirements.txt3 directories, 8 files這些是文件的內容，[~/Sandbox/pystructure]:$ cat pystructure/utils/spam.py def do():    print('hello world (from spam)!')[~/Sandbox/pystructure]:$ cat pystructure/utils/eggs/base.py def do():    print('hello world (from eggs)!')[~/Sandbox/pystructure]:$ cat pystructure/utils/eggs/__init__.py from .base import do[~/Sandbox/pystructure]:$ cat pystructure/pystructure.py #!/usr/bin/python3from .utils import spam, eggsdef main():    spam.do()    eggs.do()if __name__ == '__main__':    main()但是，當我嘗試像這樣運行應用程序時，出現此錯誤，[~/Sandbox/pystructure]:$ python3 pystructure/pystructure.py Traceback (most recent call last):  File "pystructure/pystructure.py", line 3, in <module>    from .utils import spam, eggsModuleNotFoundError: No module named '__main__.utils'; '__main__' is not a package或者當我嘗試從創建文件的目錄中運行代碼時（這不是我的愿望，因為我想將它作為服務或使用 cron 運行），[~/Sandbox/pystructure]:$ cd pystructure/[~/Sandbox/pystructure/pystructure]:$ python3 pystructure.py Traceback (most recent call last):  File "pystructure.py", line 3, in <module>    from .utils import spam, eggsModuleNotFoundError: No module named '__main__.utils'; '__main__' is not a package但是，如果我導入它，它確實可以工作（但是只能從基本目錄中...）[~/Sandbox/pystructure/pystructure]:$ cd ..[~/Sandbox/pystructure]:$ python3Python 3.6.7 (default, Oct 22 2018, 11:32:17) [GCC 8.2.0] on linuxType "help", "copyright", "credits" or "license" for more information.>>> from pystructure import pystructure>>> pystructure.main()hello world (from spam)!hello world (from eggs)!>>> 我相信我的問題來自沒有完全理解PYTHONPATH，我嘗試谷歌搜索，但我還沒有找到我的答案......請提供任何見解。