Python 动态导入 __import__

import sys,tarceback

import_str = "django.db.modle.Q"
#将会导入Q
import_calss(import_str)

#导入类库
def import_class(import_str):
    mod_str, _sep, class_str = import_str.rpartition('.')
    __import__(mod_str)
    try:
        return getattr(sys.modules[mod_str],class_str)
    except AttributeError:
        raise ImportError('Class %s cannot be found (%s)' %
                          (class_str,
                           traceback.format_exception(*sys.exc_info())))

#实例化
def import_object(import_str, *args, **kwargs):
    return import_class(import_str)(*args, **kwargs)