I plan to (attempt) to upload a flask application to a web-host that does not provide ssh access. I have confirmed that it (the webhost) will run Flask applications, and I can create one that works, when it has no database, but I am getting errors when attempting to create the database. I can't work out how to control where it is trying to place the database. My code looks like this:
from flask_sqlalchemy import SQLAlchemy
# create the extension
db = SQLAlchemy()
# create the app
app = Flask(__name__)
# configure the SQLite database, relative to the app instance folder
app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///flaskapp.db"
# initialize the app with the extension
db.init_app(app)
In my development machine, using Geany, running db.create_all() places the database in "var/app-instance/". Using PyCharm, on the same machine it places it in "instance/".
Some variable presumably dictates what this path is, but so far I haven't worked out what, or how to influence it. My application works as expected on my development server, using either development environment (Geany or Pycharm), but this does not work on the webhost I am trying to use, as described below.
As well as 'googling', I have grepped through the sqlalchemy files, and I found the def create_all(..), in schema.py but can't work out where it gets the information on what directory-structure to create.
I am not able to use "os" in the web-host, a suggestion made in other answers and tutorials. I tried creating a path in various forms, and on my development machine, this, for example, works: "sqlite:////tmp/flaskapp.db" , but I don't have access to /tmp on the web host, and I was unable to find an absolute path that the webhost would accept (ie without complaining that I don't have access to write to the directory). I can't 'pwd' on the webhost either.
Using "sqlite://instance/flaskapp.db" on my development machine produces an error pointing out that: Valid SQLite URL forms are:
- sqlite:///:memory: (or, sqlite://)
- sqlite:///relative/path/to/file.db
- sqlite:////absolute/path/to/file.db
However, if I try, a relative path, for example, "sqlite:///instance/flaskapp.db", I get "sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) unable to open database file -(Background on this error at: https://sqlalche.me/e/20/e3q8)", even if I create the directory myself (ie relative to the app.py root directory). [In this case write permissions are the same as for all other parts of the project].
That link, in the error output, says "This error is a DBAPI Error and originates from the database driver (DBAPI), not SQLAlchemy itself". Unfortunately I am not clear how to proceed from that.
If someone could help direct me to information that would help me understand and resolve the issue, that would be great, thanks!
I would like to be able to explicitly state where the database will be stored, relative to the route of my application directory
I am using Linux (Arch), in case that is important, too.
The question linked by Sam below shows the use of "url.make_url()". When I use this as shown, I get
>>> import sqlalchemy.engine.url as url
>>> url.make_url('sqlite:///flaskcw.db')
sqlite:///flaskcw.db
which is what I would expect (and what I want). But this is not what happens when I run db.create_all()
>>> from main import db
database binding
sqlite:///flaskcw.db
Engine(sqlite:////home/user/PycharmProjects/cwflaskapp/instance/flaskcw.db)
whereas I would expect it to place the database in the root of the project (in this case cwflaskapp/, as ..cwflaskapp/flaskcw.db) - given that is where main.py is - rather than in 'projroot'/instance/, a directory that is created in the process. (Or in the case of Geany in 'projroot'/var/app-instance/ - also created only on creating the database as above).
What am I missing?
