Flask app getting error of “could not locate flask application. …FLASK_APP environment variable” for Flask Migrate

Question

I have a file db_table.py that looks like:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://root:password@localhost/mydb'

db = SQLAlchemy(app)
migrate = Migrate(app, db)
.....db tables....

When I try to run:

flask db init

I get:

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

I tried first manually setting FLASK_APP var, by doing set FLASK_APP=app.py then running flask db init again, but that didn't resolve the issue.

Answer 1

The flask command line argument needs to know what module to locate the current Flask app instance in.

Set FLASK_APP as an environment variable:

export FLASK_APP=db_table.py

before running your flask command-line app.

See the Command Line Interface documentation:

For the flask script to work, an application needs to be discovered. This is achieved by exporting the FLASK_APP environment variable. It can be either set to an import path or to a filename of a Python module that contains a Flask application.

You can also set the variable per command by setting it on the same command line:

FLASK_APP=db_table.py flask db init