Python 导入错误：没有名为 Flask.myMethod 的模块

Question

I've read documentation, but I still can't quite wrap my head around how Python handles imports. I get the following error:

I've checked for circular imports (serv imports class_definitions: from class_definitions import * as well as a few other typical python modules) class_definitions.py only imports pickle I've tried rebuilding the venv I consolidated code to these two files to try to make it go away.

The most headway I got in debugging it was that if I get rid of a call to a function I defined in class_definitions.py called load_pumps() it would typically go away. I could replace the function call to a set of dummy data that represents the data load_pumps() should return and I would not get this error. load_pumps is called in other parts of the code throughout serv.py and I didn't get this error until earlier today. Any ideas?

Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 2000, in __call__
  return self.wsgi_app(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1991, in wsgi_app
response = self.make_response(self.handle_exception(e))
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1567, in handle_exception
reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1988, in wsgi_app
response = self.full_dispatch_request()
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1641, in full_dispatch_request
rv = self.handle_user_exception(e)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1544, in handle_user_exception
reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1639, in full_dispatch_request
rv = self.dispatch_request()
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1625, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/pi/Desktop/barbot/flask-files/serv.py", line 89, in admin
pump_list=load_pumps(),
  File "/home/pi/Desktop/barbot/flask-files/class_definitions.py", line 90, in load_pumps
read_pump_list = pickle.load(file_pump)
  File "/usr/lib/python2.7/pickle.py", line 1378, in load
return Unpickler(file).load()
  File "/usr/lib/python2.7/pickle.py", line 858, in load
dispatch[key](self)
  File "/usr/lib/python2.7/pickle.py", line 1090, in load_global
klass = self.find_class(module, name)
  File "/usr/lib/python2.7/pickle.py", line 1124, in find_class
__import__(module)
ImportError: No module named Flask.class_definitions

And file tree looks like this

âââ admin_config.cfg
âââ class_definitions.py
âââ class_definitions.pyc
âââ __init__.py
âââ __init__.pyc
âââ lists
â   âââ bac_list.py
â   âââ bac_list.pyc
â   âââ cocktails_all.py
â   âââ cocktails_all.pyc
â   âââ garnishes_all.lst
â   âââ garnishes_selected.lst
â   âââ __init__.py
â   âââ __init__.pyc
â   âââ mixers_all.lst
â   âââ pumps.cfg
â   âââ spirits_all.lst
âââ requirements.txt
âââ serv.py
âââ serv.pyc
âââ templates
âââ admin_console.html

2 directories, 20 files

Answer 1

It seems that you have a py file at this path:

"/home/pi/Desktop/barbot/flask-files/class_definitions.py"

And you are trying to import something named Flask.class_definitions when you pickle.load .

This fails because class_definitions is not in the Flask package.

Since you are loading a pickle, I would say you had a class_definitions module within a Flask package at some time in the past, when you created the pickle.

The way pickle works is that it saved the exact names of the classes which were used when it saves the instances, so that it can find them and reconstruct the instances when loading. If you change your code in the meantime, the pickle can become incompatible.

There are ways to implement compatibility for such situations, but instead of that I suggest that, for now at least, you dont change your class names and directory structures after saving a pickle.