python 动态引入模块 importlib 和 __import__ 不一样

如图所示，应该推荐使用 importlib 的方式。

scrapy 的源码也正是使用的这种方式

附scrapy 源码中 scrapy/utils/misc.py 中引入源码的load_object 实现

def load_object(path):
    """Load an object given its absolute object path, and return it.

    object can be a class, function, variable or an instance.
    path ie: 'scrapy.downloadermiddlewares.redirect.RedirectMiddleware'
    """

    try:
        dot = path.rindex('.')
    except ValueError:
        raise ValueError("Error loading object '%s': not a full path" % path)

    module, name = path[:dot], path[dot+1:]
    mod = import_module(module)

    try:
        obj = getattr(mod, name)
    except AttributeError:
        raise NameError("Module '%s' doesn't define any object named '%s'" % (module, name))

    return obj