__import__(name, globals=None, locals=None, fromlist=(), level=0)
用来导入模块。
>>> __import__('os')
<module 'os' from 'D:\python\python3.6\lib\os.py'>
from package import module等效于
__import__('package.module')
from module import func1,func2等效于
>>> __import__('os',fromlist='sys,system')
<module 'os' from 'D:\python\python3.6\lib\os.py'>