将main.py导入另一个模块（包含在同一目录中）

Question

如何将类从main.py导入到同一目录中的另一个文件中？

文件结构：

Project
    |-- main.py
    |-- first_file.py
    |-- second_file.py

main.py ：

class ClassX():
    def random1(self):
        ....
        return stuff

    def get(self):
        class_x_stuff = self.random1()
        print class_x_stuff

app = webapp2.WSGIApplication([
    ('/classw', ClassW),
    ('/classx', ClassX)
], debug=True)

first_file.py ：

import main

checkpoint = main.ClassX()
print checkout

输出：

AttributeError: 'module' object has no attribute 'ClassX'

我使用的资源：

1. 如何在同一目录或子目录中导入类？
2. AttributeError：“模块”对象没有属性

我可以将first_file.py导入main.py以及second_file.py 。 但是我无法将main.py导入其他文件。

重命名main.py文件（例如proj_main.py ）会导致错误：

Traceback (most recent call last):
File "/usr/local/google_appengine/google/appengine/runtime/wsgi.py", line 240, in Handle
  handler = _config_handle.add_wsgi_middleware(self._LoadHandler())
File "/usr/local/google_appengine/google/appengine/runtime/wsgi.py", line 299, in _LoadHandler
  handler, path, err = LoadObject(self._handler)
File "/usr/local/google_appengine/google/appengine/runtime/wsgi.py", line 85, in LoadObject
  obj = __import__(path[0])

ImportError: No module named main

我有什么选择？ 我该如何解决这个问题？

编辑：

完整回溯：

INFO     2017-10-02 22:10:21,744 dispatcher.py:226] Starting module "default" running at: http://localhost:7070
INFO     2017-10-02 22:10:21,747 admin_server.py:116] Starting admin server at: http://localhost:8000
ERROR    2017-10-02 22:10:24,017 wsgi.py:263] 
Traceback (most recent call last):
  File "/usr/local/google_appengine/google/appengine/runtime/wsgi.py", line 240, in Handle
handler = _config_handle.add_wsgi_middleware(self._LoadHandler())
  File "/usr/local/google_appengine/google/appengine/runtime/wsgi.py", line 299, in _LoadHandler
handler, path, err = LoadObject(self._handler)
  File "/usr/local/google_appengine/google/appengine/runtime/wsgi.py", line 85, in LoadObject
obj = __import__(path[0])
  File "/Users/mycomputer/Documents/project_folder/main.py", line 34, in <module>
from first_file import ClassY
  File "/Users/mycomputer/Documents/project_folder/first_file.py", line 20, in <module>
    checkpoint = main.ClassX()
AttributeError: 'module' object has no attribute ‘ClassX’
INFO     2017-10-02 22:10:24,023 module.py:832] default: "GET / HTTP/1.1" 500 -

Answer 1

问题是我遇到了循环依赖 ：

File "/Users/mycomputer/Documents/project_folder/main.py", line 34, in <module>
from first_file import ClassY

请注意， main.py是从first_file导入的，然后first_file是从main.py导入的，这导致了循环导入 main.py 。

解：

first_file.py

import second_file

checkpoint = second_file.class_x()
    print checkout

second_file.py

import main

def class_x():
    item = main.ClassX()
    return item