python之importlib模块
2021-05-17 12:28
标签：ring ogg eve design let ast 使用 实现 prope 解析字符串，并导入改路径的模块 从"aa.bb"路径导入bb模块。 在Django源码目录"django/utils/module_loading.py",使用importlib中的import_module函数实现了Django中自定义的import_string(dotted_path)方法 源码： 解析： 例如Django项目settings.py中的‘django.middleware.clickjacking.XFrameOptionsMiddleware‘，在dotted_path.rsplit(‘.‘, 1)后生成元组(‘django.middleware.clickjacking‘,‘XFrameOptionsMiddleware‘),再使用import_module导入‘django.middleware.clickjacking‘模块，最后使用映射获取类XFrameOptionsMiddleware。 在"django\core\handlers\base.py"中class BaseHandler中有load_middleware()方法用来导入settings中的中间件，其中调用了上面的import_string()方法，源码如下： python之importlib模块 标签：ring ogg eve design let ast 使用 实现 prope 原文地址：https://www.cnblogs.com/bad-robot/p/9746870.html1、import_module方法
# 根据字符串导入模块
# 通畅用来导入包下面的模块
o = importlib.import_module("aa.bb")
s2 = "Person"
# 由字符串找函数、方法、类 利用 反射
the_class = getattr(o, "Person")
p2 = the_class("小黑")
p2.dream()
2、import_module在Django中的使用
2.1、Django中使用import_module实现import_string方法
def import_string(dotted_path):
"""
Import a dotted module path and return the attribute/class designated by the
last name in the path. Raise ImportError if the import failed.
"""
try:
module_path, class_name = dotted_path.rsplit(‘.‘, 1)
except ValueError as err:
raise ImportError("%s doesn‘t look like a module path" % dotted_path) from err
module = import_module(module_path)
try:
return getattr(module, class_name)
except AttributeError as err:
raise ImportError(‘Module "%s" does not define a "%s" attribute/class‘ % (
module_path, class_name)
) from err
2.2、Django中使用import_string导入模块中的类
def load_middleware(self):
"""
Populate middleware lists from settings.MIDDLEWARE.
Must be called after the environment is fixed (see __call__ in subclasses).
"""
self._request_middleware = []
self._view_middleware = []
self._template_response_middleware = []
self._response_middleware = []
self._exception_middleware = []
handler = convert_exception_to_response(self._get_response)
for middleware_path in reversed(settings.MIDDLEWARE):
middleware = import_string(middleware_path)
try:
mw_instance = middleware(handler)
except MiddlewareNotUsed as exc:
if settings.DEBUG:
if str(exc):
logger.debug(‘MiddlewareNotUsed(%r): %s‘, middleware_path, exc)
else:
logger.debug(‘MiddlewareNotUsed: %r‘, middleware_path)
continue
if mw_instance is None:
raise ImproperlyConfigured(
‘Middleware factory %s returned None.‘ % middleware_path
)
if hasattr(mw_instance, ‘process_view‘):
self._view_middleware.insert(0, mw_instance.process_view)
if hasattr(mw_instance, ‘process_template_response‘):
self._template_response_middleware.append(mw_instance.process_template_response)
if hasattr(mw_instance, ‘process_exception‘):
self._exception_middleware.append(mw_instance.process_exception)
handler = convert_exception_to_response(mw_instance)
# We only assign to this when initialization is complete as it is used
# as a flag for initialization being complete.
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