flask.cli.NoAppException: The file/path provided (new_app.py) does not appear to exist

flask.cli.NoAppException: The file/path provided (new_app.py) does not appear to exist - python

I keep getting this error flask.cli.NoAppException: The file/path provided (new_app.py) does not appear to exist. Please verify the path is correct. If app is not on PYTHONPATH, ensure the extension is .py it goes away after I restart the Flask server.
I am running flask run in the correct directory where my app is. This just started happening after working for 2 weeks. I've read that it could be due to an import error, but I am not finding any modules that are not installed on my virutalenv.
from flask import Flask
app = Flask(__name__)
app.debug=True

Most likely you haven't set the FLASK_APP environment variable.
To run the application you can either use the flask command or
python’s -m switch with Flask. Before you can do that you need to tell
your terminal the application to work with by exporting the FLASK_APP
environment variable:
$ export FLASK_APP=hello.py
$ flask run * Running on http://127.0.0.1:5000/
If you are on Windows you need to use set
instead of export.
Alternatively you can use python -m flask:
$ export FLASK_APP=hello.py
$ python -m flask run * Running on http://127.0.0.1:5000/
EDIT
If you have FLASK_APP set then try adding this to new_app.py
app.run(debug=True, port=8800)
Or if you're on Windows:
if __name__ == '__main__':
app.run(debug=True, port=8800)
And then just execute the app with python new_app.py.

Related

Python win32api.MessageBox and Tk are not showing up when python program activated by IIS [duplicate]

How are you meant to debug errors in Flask? Print to the console? Flash messages to the page? Or is there a more powerful option available to figure out what's happening when something goes wrong?

Running the app in debug mode will show an interactive traceback and console in the browser when there is an error. As of Flask 2.2, to run in debug mode, pass the --app and --debug options to the flask command.
$ flask --app example --debug run
Prior to Flask 2.2, this was controlled by the FLASK_ENV=development environment variable instead. You can still use FLASK_APP and FLASK_DEBUG=1 instead of the options above.
For Linux, Mac, Linux Subsystem for Windows, Git Bash on Windows, etc.:
$ export FLASK_APP=example
$ export FLASK_DEBUG=1
$ flask run
For Windows CMD, use set instead of export:
set FLASK_DEBUG=1
For PowerShell, use $env:
$env:FLASK_DEBUG = "1"
If you're using the app.run() method instead of the flask run command, pass debug=True to enable debug mode.
Tracebacks are also printed to the terminal running the server, regardless of development mode.
If you're using PyCharm, VS Code, etc., you can take advantage of its debugger to step through the code with breakpoints. The run configuration can point to a script calling app.run(debug=True, use_reloader=False), or point it at the venv/bin/flask script and use it as you would from the command line. You can leave the reloader disabled, but a reload will kill the debugging context and you will have to catch a breakpoint again.
You can also use pdb, pudb, or another terminal debugger by calling set_trace in the view where you want to start debugging.
Be sure not to use too-broad except blocks. Surrounding all your code with a catch-all try... except... will silence the error you want to debug. It's unnecessary in general, since Flask will already handle exceptions by showing the debugger or a 500 error and printing the traceback to the console.

You can use app.run(debug=True) for the Werkzeug Debugger edit as mentioned below, and I should have known.

From the 1.1.x documentation, you can enable debug mode by exporting an environment variable to your shell prompt:
export FLASK_APP=/daemon/api/views.py # path to app
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0

One can also use the Flask Debug Toolbar extension to get more detailed information embedded in rendered pages.
from flask import Flask
from flask_debugtoolbar import DebugToolbarExtension
import logging
app = Flask(__name__)
app.debug = True
app.secret_key = 'development key'
toolbar = DebugToolbarExtension(app)
#app.route('/')
def index():
logging.warning("See this message in Flask Debug Toolbar!")
return "<html><body></body></html>"
Start the application as follows:
FLASK_APP=main.py FLASK_DEBUG=1 flask run

If you're using Visual Studio Code, replace
app.run(debug=True)
with
app.run()
It appears when turning on the internal debugger disables the VS Code debugger.

If you want to debug your flask app then just go to the folder where flask app is. Don't forget to activate your virtual environment and paste the lines in the console change "mainfilename" to flask main file.
export FLASK_APP="mainfilename.py"
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0
After you enable your debugger for flask app almost every error will be printed on the console or on the browser window.
If you want to figure out what's happening, you can use simple print statements or you can also use console.log() for javascript code.

To activate debug mode in flask you simply type set FLASK_DEBUG=1 on your CMD for windows, or export FLASK_DEBUG=1 on Linux terminal then restart your app and you are good to go!!

Install python-dotenv in your virtual environment.
Create a .flaskenv in your project root. By project root, I mean the folder which has your app.py file
Inside this file write the following:
FLASK_APP=myapp
FLASK_ENV=development
Now issue the following command:
flask run

When running as python app.py instead of the flask command, you can pass debug=True to app.run.
if __name__ == "__main__":
app.run(debug=True)
$ python app.py

with virtual env activate
export FLASK_DEBUG=true
you can configure
export FLASK_APP=app.py # run.py
export FLASK_ENV = "development"
to start
flask run
the result
* Environment: development
* Debug mode: on
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: xxx-xxx-xxx
and if you change
export FLASK_DEBUG=false
* Environment: development
* Debug mode: off
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

For Windows users:
Open Powershell and cd into your project directory.
Use these commandos in Powershell, all the other stuff won't work in Powershell.
$env:FLASK_APP = "app"
$env:FLASK_ENV = "development"

If you have PyCharm Professional, you can create a Flask server run configuration and enable the FLASK_DEBUG checkbox. Go to Run > Edit Configurations, select or create a Flask server configuration, and enable the FLASK_DEBUG checkbox. Click OK, then click the run button.

You can install python-dotenv with
pip install python-dotenv then create a .flask_env or a .env file
The contents of the file can be:
FLASK_APP=myapp
FLASK_DEBUG=True

Use loggers and print statements in the Development Environment, you can go for sentry in case of production environments.

What do I change or add when receiving Internal Server error? [duplicate]

How are you meant to debug errors in Flask? Print to the console? Flash messages to the page? Or is there a more powerful option available to figure out what's happening when something goes wrong?

You can use app.run(debug=True) for the Werkzeug Debugger edit as mentioned below, and I should have known.

From the 1.1.x documentation, you can enable debug mode by exporting an environment variable to your shell prompt:
export FLASK_APP=/daemon/api/views.py # path to app
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0

One can also use the Flask Debug Toolbar extension to get more detailed information embedded in rendered pages.
from flask import Flask
from flask_debugtoolbar import DebugToolbarExtension
import logging
app = Flask(__name__)
app.debug = True
app.secret_key = 'development key'
toolbar = DebugToolbarExtension(app)
#app.route('/')
def index():
logging.warning("See this message in Flask Debug Toolbar!")
return "<html><body></body></html>"
Start the application as follows:
FLASK_APP=main.py FLASK_DEBUG=1 flask run

If you're using Visual Studio Code, replace
app.run(debug=True)
with
app.run()
It appears when turning on the internal debugger disables the VS Code debugger.

If you want to debug your flask app then just go to the folder where flask app is. Don't forget to activate your virtual environment and paste the lines in the console change "mainfilename" to flask main file.
export FLASK_APP="mainfilename.py"
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0
After you enable your debugger for flask app almost every error will be printed on the console or on the browser window.
If you want to figure out what's happening, you can use simple print statements or you can also use console.log() for javascript code.

To activate debug mode in flask you simply type set FLASK_DEBUG=1 on your CMD for windows, or export FLASK_DEBUG=1 on Linux terminal then restart your app and you are good to go!!

Install python-dotenv in your virtual environment.
Create a .flaskenv in your project root. By project root, I mean the folder which has your app.py file
Inside this file write the following:
FLASK_APP=myapp
FLASK_ENV=development
Now issue the following command:
flask run

When running as python app.py instead of the flask command, you can pass debug=True to app.run.
if __name__ == "__main__":
app.run(debug=True)
$ python app.py

with virtual env activate
export FLASK_DEBUG=true
you can configure
export FLASK_APP=app.py # run.py
export FLASK_ENV = "development"
to start
flask run
the result
* Environment: development
* Debug mode: on
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: xxx-xxx-xxx
and if you change
export FLASK_DEBUG=false
* Environment: development
* Debug mode: off
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

For Windows users:
Open Powershell and cd into your project directory.
Use these commandos in Powershell, all the other stuff won't work in Powershell.
$env:FLASK_APP = "app"
$env:FLASK_ENV = "development"

If you have PyCharm Professional, you can create a Flask server run configuration and enable the FLASK_DEBUG checkbox. Go to Run > Edit Configurations, select or create a Flask server configuration, and enable the FLASK_DEBUG checkbox. Click OK, then click the run button.

You can install python-dotenv with
pip install python-dotenv then create a .flask_env or a .env file
The contents of the file can be:
FLASK_APP=myapp
FLASK_DEBUG=True

Use loggers and print statements in the Development Environment, you can go for sentry in case of production environments.

Internal Server Error while executing a flask module [duplicate]

How are you meant to debug errors in Flask? Print to the console? Flash messages to the page? Or is there a more powerful option available to figure out what's happening when something goes wrong?

You can use app.run(debug=True) for the Werkzeug Debugger edit as mentioned below, and I should have known.

From the 1.1.x documentation, you can enable debug mode by exporting an environment variable to your shell prompt:
export FLASK_APP=/daemon/api/views.py # path to app
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0

One can also use the Flask Debug Toolbar extension to get more detailed information embedded in rendered pages.
from flask import Flask
from flask_debugtoolbar import DebugToolbarExtension
import logging
app = Flask(__name__)
app.debug = True
app.secret_key = 'development key'
toolbar = DebugToolbarExtension(app)
#app.route('/')
def index():
logging.warning("See this message in Flask Debug Toolbar!")
return "<html><body></body></html>"
Start the application as follows:
FLASK_APP=main.py FLASK_DEBUG=1 flask run

If you're using Visual Studio Code, replace
app.run(debug=True)
with
app.run()
It appears when turning on the internal debugger disables the VS Code debugger.

If you want to debug your flask app then just go to the folder where flask app is. Don't forget to activate your virtual environment and paste the lines in the console change "mainfilename" to flask main file.
export FLASK_APP="mainfilename.py"
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0
After you enable your debugger for flask app almost every error will be printed on the console or on the browser window.
If you want to figure out what's happening, you can use simple print statements or you can also use console.log() for javascript code.

To activate debug mode in flask you simply type set FLASK_DEBUG=1 on your CMD for windows, or export FLASK_DEBUG=1 on Linux terminal then restart your app and you are good to go!!

Install python-dotenv in your virtual environment.
Create a .flaskenv in your project root. By project root, I mean the folder which has your app.py file
Inside this file write the following:
FLASK_APP=myapp
FLASK_ENV=development
Now issue the following command:
flask run

When running as python app.py instead of the flask command, you can pass debug=True to app.run.
if __name__ == "__main__":
app.run(debug=True)
$ python app.py

with virtual env activate
export FLASK_DEBUG=true
you can configure
export FLASK_APP=app.py # run.py
export FLASK_ENV = "development"
to start
flask run
the result
* Environment: development
* Debug mode: on
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: xxx-xxx-xxx
and if you change
export FLASK_DEBUG=false
* Environment: development
* Debug mode: off
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

For Windows users:
Open Powershell and cd into your project directory.
Use these commandos in Powershell, all the other stuff won't work in Powershell.
$env:FLASK_APP = "app"
$env:FLASK_ENV = "development"

If you have PyCharm Professional, you can create a Flask server run configuration and enable the FLASK_DEBUG checkbox. Go to Run > Edit Configurations, select or create a Flask server configuration, and enable the FLASK_DEBUG checkbox. Click OK, then click the run button.

You can install python-dotenv with
pip install python-dotenv then create a .flask_env or a .env file
The contents of the file can be:
FLASK_APP=myapp
FLASK_DEBUG=True

Use loggers and print statements in the Development Environment, you can go for sentry in case of production environments.

Error: Could not locate a Flask application in VSCode

I am trying to learn Flask using VScode.
The tutorial that I am following is: Python Flask Tutorial: Full-Featured Web App Part 1 - Getting Started.
I did the following things:
Created a new virtualenv in a folder using: virtualenv venv
activated it as: venv\Scripts\activate (I am on Windows 10)
After that, I created a new directory named Flask_Blog using mkdir Flask_Blog and in it, I created a new flaskblog.py file containing the following code:
from flask import Flask
app = Flask(__name__)
#app.route('/')
def hello():
return 'Hello'
Then, in the terminal of VScode, I changed my working directory in order to be in the Flask_Blog directory using cd Flask_Blog.
Now, when I am doing set FLASK_APP=flaskblog.py followed by flask run, I am getting the following error:
(venv) PS C:\Users\kashy\OneDrive\Desktop\Flask\Flask_Blog> flask run
* Environment: production
WARNING: This is a development server. Do not use it in a production deployment.
Use a production WSGI server instead.
* Debug mode: off
Usage: flask run [OPTIONS]
Error: Could not locate a Flask application. You did not provide the "FLASK_APP" environment variable, and a "wsgi.py" or "app.py" module was not found in the current directory.
But
When I do the same in the cmd prompt, the code runs and I get to see the output.
I am completely new to this. Can anyone please tell me what is the mistake I am doing in VSCode and why is it working in the cmd?

Issue raised in VsCode
Under Powershell, you have to set the FLASK_APP environment variable as follows:
$env:FLASK_APP = "webapp"
Then you should be able to run "python -m flask run" inside the hello_app folder. In other words, PowerShell manages environment variables differently, so the standard command-line "set FLASK_APP=webapp" won't work.

Try Set FLASK_APP = Full path of the folder/filename.py.
This worked for me

This worked for me on the VSCode:
$env:FLASK_APP= 'C:\Python\ex003\main:app'

Make flask run honor app.debug [duplicate]

How are you meant to debug errors in Flask? Print to the console? Flash messages to the page? Or is there a more powerful option available to figure out what's happening when something goes wrong?

You can use app.run(debug=True) for the Werkzeug Debugger edit as mentioned below, and I should have known.

From the 1.1.x documentation, you can enable debug mode by exporting an environment variable to your shell prompt:
export FLASK_APP=/daemon/api/views.py # path to app
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0

One can also use the Flask Debug Toolbar extension to get more detailed information embedded in rendered pages.
from flask import Flask
from flask_debugtoolbar import DebugToolbarExtension
import logging
app = Flask(__name__)
app.debug = True
app.secret_key = 'development key'
toolbar = DebugToolbarExtension(app)
#app.route('/')
def index():
logging.warning("See this message in Flask Debug Toolbar!")
return "<html><body></body></html>"
Start the application as follows:
FLASK_APP=main.py FLASK_DEBUG=1 flask run

If you're using Visual Studio Code, replace
app.run(debug=True)
with
app.run()
It appears when turning on the internal debugger disables the VS Code debugger.

If you want to debug your flask app then just go to the folder where flask app is. Don't forget to activate your virtual environment and paste the lines in the console change "mainfilename" to flask main file.
export FLASK_APP="mainfilename.py"
export FLASK_DEBUG=1
python -m flask run --host=0.0.0.0
After you enable your debugger for flask app almost every error will be printed on the console or on the browser window.
If you want to figure out what's happening, you can use simple print statements or you can also use console.log() for javascript code.

To activate debug mode in flask you simply type set FLASK_DEBUG=1 on your CMD for windows, or export FLASK_DEBUG=1 on Linux terminal then restart your app and you are good to go!!

Install python-dotenv in your virtual environment.
Create a .flaskenv in your project root. By project root, I mean the folder which has your app.py file
Inside this file write the following:
FLASK_APP=myapp
FLASK_ENV=development
Now issue the following command:
flask run

When running as python app.py instead of the flask command, you can pass debug=True to app.run.
if __name__ == "__main__":
app.run(debug=True)
$ python app.py

with virtual env activate
export FLASK_DEBUG=true
you can configure
export FLASK_APP=app.py # run.py
export FLASK_ENV = "development"
to start
flask run
the result
* Environment: development
* Debug mode: on
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
* Restarting with stat
* Debugger is active!
* Debugger PIN: xxx-xxx-xxx
and if you change
export FLASK_DEBUG=false
* Environment: development
* Debug mode: off
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

For Windows users:
Open Powershell and cd into your project directory.
Use these commandos in Powershell, all the other stuff won't work in Powershell.
$env:FLASK_APP = "app"
$env:FLASK_ENV = "development"

If you have PyCharm Professional, you can create a Flask server run configuration and enable the FLASK_DEBUG checkbox. Go to Run > Edit Configurations, select or create a Flask server configuration, and enable the FLASK_DEBUG checkbox. Click OK, then click the run button.

You can install python-dotenv with
pip install python-dotenv then create a .flask_env or a .env file
The contents of the file can be:
FLASK_APP=myapp
FLASK_DEBUG=True

Use loggers and print statements in the Development Environment, you can go for sentry in case of production environments.

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