Python项目结构,项目主文件导入助手

这是我的项目结构.

[~/Sandbox/pystructure]:$tree
.
├── pystructure
│   ├── __init__.py
│?? ├── pystructure.py
│?? └── utils
│??     ├── eggs
│??     │?? ├── base.py
│??     │?? └── __init__.py
│??     ├── __init__.py
│??     └── spam.py
├── README.md
└── requirements.txt

3 directories,8 files

这些是文件的内容,

[~/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/python3

from .utils import spam,eggs

def main():
    spam.do()
    eggs.do()

if __name__ == '__main__':
    main()

但是,当我尝试像这样运行应用程序时,出现此错误,

[~/Sandbox/pystructure]:$python3 pystructure/pystructure.py 
Traceback (most recent call last):
  File "pystructure/pystructure.py",line 3,in <module>
    from .utils import spam,eggs
ModuleNotFoundError: No module named '__main__.utils'; '__main__' is not a package

或者当我尝试从创建文件的目录中运行代码时(这不是我的期望,因为我想将其作为服务或使用cron来运行),

[~/Sandbox/pystructure]:$cd pystructure/

[~/Sandbox/pystructure/pystructure]:$python3 pystructure.py 
Traceback (most recent call last):
  File "pystructure.py",eggs
ModuleNotFoundError: No module named '__main__.utils'; '__main__' is not a package

但是,如果我导入它,它确实可以工作(但是只能从基本目录中…)

[~/Sandbox/pystructure/pystructure]:$cd ..

[~/Sandbox/pystructure]:$python3
Python 3.6.7 (default,Oct 22 2018,11:32:17) 
[GCC 8.2.0] on linux
Type "help","copyright","credits" or "license" for more information.
>>> from pystructure import pystructure
>>> pystructure.main()
hello world (from spam)!
hello world (from eggs)!
>>> 

(如果我尝试从它所在的目录中导入它,则会收到此错误),

[~/Sandbox/pystructure]:$cd pystructure/

[~/Sandbox/pystructure/pystructure]:$python3
Python 3.6.7 (default,"credits" or "license" for more information.
>>> import pystructure
Traceback (most recent call last):
  File "<stdin>",line 1,in <module>
  File "~/Sandbox/pystructure/pystructure/pystructure.py",eggs
ImportError: attempted relative import with no known parent package
>>> 

我相信我的问题来自对PYTHONPATH的不完全了解,我尝试使用Google谷歌搜索,但是我还没有找到答案…请提供任何见解.