Flask view raises TypeError: 'bool' object is not callable
flask, flask-login, python
Solution
In Flask, a view must return one of the following:
- a string
- a `Response` object (or subclass)
- a tuple of `(string, status, headers)` or `(string, status)`
- a valid WSGI application
Flask tests for the first 3 options, and if they don't fit, assumes it is the fourth. You returned True somewhere, and it is being treated as a WSGI application instead.
See About Responses in the documentation.
Problem
I am trying to debug a view in my Flask app that is return a 500 status with the error `TypeError: 'bool' object is not callable` in the traceback. The view calls `login_user` from Flask-Login then returns `True` to indicate that the login was successful. I have debugged until `app_iter = app(environ, start_response)` and the `app` is now a boolean with the value `True` rather than the Flask app object. ``` Traceback (most recent call last): File "D:\Python27\lib\site-packages\flask\app.py", line 1836, in __call__ return self.wsgi_app(environ, start_response) File "D:\Python27\lib\site-packages\flask\app.py", line 1820, in wsgi_app response = self.make_response(self.handle_exception(e)) File "D:\Python27\lib\site-packages\flask\app.py", line 1403, in handle_exception reraise(exc_type, exc_value, tb) File "D:\Python27\lib\site-packages\flask\app.py", line 1817, in wsgi_app response = self.full_dispatch_request() File "D:\Python27\lib\site-packages\flask\app.py", line 1478, in full_dispatch_request response = self.make_response(rv) File "D:\Python27\lib\site-packages\flask\app.py", line 1577, in make_response rv = self.response_class.force_type(rv, request.environ) File "D:\Python27\lib\site-packages\werkzeug\wrappers.py", line 824, in force_type response = BaseResponse(*_run_wsgi_app(response, environ)) File "D:\Python27\lib\site-packages\werkzeug\wrappers.py", line 57, in _run_wsgi_app return _run_wsgi_app(*args) File "D:\Python27\lib\site-packages\werkzeug\test.py", line 854, in run_wsgi_app app_iter = app(environ, start_response) TypeError: 'bool' object is not callable ``` ``` @app.route('/login', methods=['POST']) def login(): username = request.form['username'] user = User.query.filter_by(username=username).first() if user: login_user(user) return True return False ```