Flask AssertionError: View function mapping is overwriting an existing endpoint function: index

Question

My first hello world program is not working.

This is my code:

from flask import Flask
app=Flask(__name__)
@app.route('/')
def index():
    return "<h1>Hello world</h1>"

if __name__=='__main__':
        app.run()
 

And this is my output:

(myflaskenv) C:\Users\saini computers\Desktop\flask_examples>python 
 basic.py
Traceback (most recent call last):
  File "basic.py", line 6, in <module>
    @app.route('/information')
  File "C:\Users\saini computers\Anaconda3\envs\myflaskenv\lib\site- 
  packages\flask\app.py", line 1250, in decorator
    self.add_url_rule(rule, endpoint, f, **options)
  File "C:\Users\saini computers\Anaconda3\envs\myflaskenv\lib\site- 
  packages\flask\app.py", line 66, in wrapper_func
    return f(self, *args, **kwargs)
  File "C:\Users\saini computers\Anaconda3\envs\myflaskenv\lib\site- 
  packages\flask\app.py", line 1221, in add_url_rule
    'existing endpoint function: %s' % endpoint)

AssertionError: View function mapping is overwriting an existing endpoint function: index

Answer 1

AssertionError: View function mapping is overwriting an existing endpoint function: index

This error indicates that you have used same method name in multiple routes.

You can reproduce the error using the following code:

from flask import Flask

app = Flask(__name__)

@app.route("/")
def index():
    return "hello from index"

@app.route("/info")
def index():
    return "hello from info"

app.run(debug=True, port=8080)

Error trace:

(venv) ? python app.py 
Traceback (most recent call last):
  File "app.py", line 9, in <module>
    @app.route("/info", methods=['GET'])
  File ".../app.py", line 1250, in decorator
    self.add_url_rule(rule, endpoint, f, **options)
  File ".../app.py", line 66, in wrapper_func
    return f(self, *args, **kwargs)
  File ".../app.py", line 1221, in add_url_rule
    'existing endpoint function: %s' % endpoint)
AssertionError: View function mapping is overwriting an existing endpoint function: index

Both routes @app.route("/info") and @app.route("/") use same method called index. So I am getting the error: AssertionError: View function mapping is overwriting an existing endpoint function: index

I think, you are making same mistake. You are using method index for both / and /information route.

Answer 2

As of version 4.x.x, it is now @jwt_required() instead of jwt_required. If you are updating an existing application, you can find a link to all of the breaking changes in the 4.x.x release on the README.