Flask says "did not provide the FLASK_APP environment variable"

Question

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?

Answer 1

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.