AssertionError View function mapping is overwriting an existing endpoint function main

Question

Does anyone know why I can t overwrite an existing endpoint function if i have two url rules like this  app add url rule                       view func Main as view  main                     methods   GET     app add url rule    lt page gt                      view func Main as view  main                     methods   GET      Traceback   Traceback  most recent call last      File  demo py   line 20  in  lt module gt  methods   GET       File      python2 6 site-packages flask   app py        line 62  in wrapper func return f self   args    kwargs     File      python2 6 site-packages flask   app py        line 984  in add url rule  existing endpoint function   s    endpoint    AssertionError  View function mapping is overwriting an existing endpoint      function  main

User · Accepted Answer

Your view names need to be unique even if they are pointing to the same view method   app add url rule                       view func Main as view  main                     methods     GET     app add url rule    lt page gt                      view func Main as view  page                     methods     GET

User · Answer

There is a fix for Flask issue  570 introduced recenty  flask 0 10  that causes this exception to be raised   See https   github com mitsuhiko flask issues 796  So if you go to flask app py and comment out the 4 lines 948  951  this may help until the issue is resovled fully in a new version   The diff of that change is here  http   github com mitsuhiko flask commit 661ee54bc2bc1ea0763ac9c226f8e14bb0beb5b1

User · Answer

For users that use  app route it is better to use the key-argument endpoint rather then chaning the value of   name   like Roei Bahumi stated  Taking his example will be    app route   path1   endpoint  func1    exception handler def func1        pass   app route   path2   endpoint  func2    exception handler def func2        pass

User · Answer

Your view names need to be unique even if they are pointing to the same view method  or you can add from functools import wraps and use  wraps https   docs python org 2 library functools html

User · Answer

Flask requires you to associate a single  view function  with an  endpoint   You are calling Main as view  main   twice which creates two different functions  exactly the same functionality but different in memory signature   Short story  you should simply do  main view func   Main as view  main    app add url rule                   view func main view func               methods   GET     app add url rule    lt page gt                  view func main view func               methods   GET

User · Answer

I would just like to add to this a more  template  type solution   def func name f       def wrap  args    kwargs           if condition              pass         else              whatever you want         return f  args    kwargs      wrap   name     f   name       return wrap   would just like to add a really interesting article  Demystifying Decorators  I found recently  https   sumit-ghosh com articles demystifying-decorators-python

User · Answer

Adding  wraps f  above the wrapper function solved my issue  def list ownership f        wraps f      def decorator  args   kwargs           return f args kwargs      return decorator

User · Answer

If you think you have unique endpoint names and still this error is given then probably you are facing issue  Same was the case with me   This issue is with flask 0 10 in case you have same version then do following to get rid of this   sudo pip uninstall flask sudo pip install flask 0 9

User · Answer

This can happen also when you have identical function names on different routes

User · Answer

use flask 0 9 instead use the following commands sudo pip uninstall flask  sudo pip install flask  0 9

User · Answer

This same issue happened to me when I had more than one API function in the module and tried to wrap each function with 2 decorators     app route   My custom  exception handler decorator   I got this same exception because I tried to wrap more than one function with those two decorators     app route   path1    exception handler def func1        pass   app route   path2    exception handler def func2        pass   Specifically  it is caused by trying to register a few functions with the name wrapper   def exception handler func     def wrapper  args    kwargs       try          return func  args    kwargs      except Exception as e          error code   getattr e   code   500          logger exception  Service exception   s   e          r   dict to json   message   e message   matches   e message   error code   error code           return Response r  status error code  mimetype  application json     return wrapper   Changing the name of the function solved it for me  wrapper   name     func   name      def exception handler func     def wrapper  args    kwargs       try          return func  args    kwargs      except Exception as e          error code   getattr e   code   500          logger exception  Service exception   s   e          r   dict to json   message   e message   matches   e message   error code   error code           return Response r  status error code  mimetype  application json       Renaming the function name    wrapper   name     func   name     return wrapper   Then  decorating more than one endpoint worked

[python] AssertionError: View function mapping is overwriting an existing endpoint function: main

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