Flask says "did not provide the FLASK_APP environment variable"

I'm trying to run a Flask application with flask run but no matter what, I receive this error:

Error: Could not locate Flask application. You did not provide the FLASK_APP environment variable. 

I'm using virtualenv in my project and I'm running the app on port 80 so I run the command as superuser. Ultimately, I just need to use the flask db init command as described in Flask-Migrate's docs, but flask needs to be able to find the app to do that. Here's what I've tried, with no success:

Exporting the FLASK_APP environment variable, ensuring that it's in my bash profile, then activating virtualenv

$ export FLASK_APP=run.py $ printenv FLASK_APP run.py $ . env/bin/activate (env) $ sudo flask run Error: Could not locate Flask application. You did not provide the FLASK_APP environment variable. 

Activating virtualenv, then exporting FLASK_APP

$ . env/bin/activate (env) $ export FLASK_APP=run.py (env) $ printenv FLASK_APP run.py (env) sudo flask run Error: Could not locate Flask application. You did not provide the FLASK_APP environment variable. 

The above two with the full path, /Users/me/code/project/run.py

$ printenv FLASK_APP /Users/me/code/project/run.py 

Project Structure

myproject/ ├──app/ | ├── __init__.py | ├── models.py | ├── templates/ | └── views.py ├── tests/ ├── run.py ├── requirements.txt └── config.py 

So far nothing has worked and the error message is the same in each case. What can I do to fix this error?

6 Answers

If you are on Windows, make sure there is no space around the equal :

set FLASK_APP=app.py 

instead of

set FLASK_APP = app.py 

That's what happened to me. I got the " You did not provide the FLASK_APP environment variable" error because of the spaces.

Assuming you call app=App(__name__) in your init file. Try this, even though technically it should work with run.py as-well.

export FLASK_APP=app/__init__.py; flask run 

Also try doing an echo $FLASK_APP later to see if the value actually gets stored in the environment variable which flask directly accesses and not only the bash profile.

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.

When I drop sudo from sudo flask run, Flask finds $FLASK_APP. However, I get the error message socket.error: [Errno 13] Permission denied. I can't see a way around this, as Flask cannot find $FLASK_APP when I run as superuser. Seems like circular logic.

I've managed to run Flask by changing the port from 80 to 5000 and dropping sudo with flask run. This is fine, I will have to find a way to run the app on port 80 in production though.

I was able to run flask db init after dropping and recreating my database, and removing calls to db.create_all.

Edit - 4/27/17 port 80 was indeed blocked by the firewall on my server (the firewall is beyond my control) so running the app on an open port resolved the issue.

looks you are using bash shell in your terminal. read the flask 2.0 docs. the command should be export FLASK_APP=run and it will have no extension

I faced the same issue. I am using Python 3.10 in VS code.

C:\Users\hansr>flask --version Python 3.10.1 Flask 2.0.3 Werkzeug 2.0.3 

USING set FLASK_APP='main.py' did not work for me and throws the same mentioned error above.

TRY:

$env:FLASK_APP = "main" python -m flask run 

REFERENCE