python importsystem

https://docs.python.org/3/reference/import.html#importsystem

導入模塊的三個方法:
1.import 關鍵字
2.importlib.import_module()
3.__import__()

import本質上調用__import()__方法

屬性	描述
__name__	模塊的名稱(文件名),如果是入口,則爲__main__
__loader__	The loader attribute must be set to the loader object that the import machinery used when loading the module
__package__	頂層的package名
__spec__
__path__	如果module包含__path__屬性,則他是一個package
__file__	module的絕對路徑
__cached__

package相對導入

package/
    __init__.py
    subpackage1/
        __init__.py
        moduleX.py
        moduleY.py
    subpackage2/
        __init__.py
        moduleZ.py
    moduleA.py

In either subpackage1/moduleX.py or subpackage1/init.py, the following are valid relative imports:

from .moduleY import spam
from .moduleY import spam as ham
from . import moduleY
from ..subpackage1 import moduleY
from ..subpackage2.moduleZ import eggs
from ..moduleA import foo

參考:
package和namespace package
https://blog.csdn.net/chaoguo1234/article/details/81277587