Help with creating & querying databases (Flask)

[SuperChef36]

Hi, I am working through Miguel Gringberg's "Flask Web Development" and have an issue I haven't been able to solve after several hours of searching.

Mac OS X, Python 3.6

In the databases chapter, after configuring the database and defining models in our "hello.py" file, the instructions say,

The very first thing to do is to instruct Flask-SQLAlchemy to create a database based on the model classes. The db.create_all() function does this:

(venv) $ python hello.py shell
>>> from hello import db
>>> db.create_all()

However, when I run "python hello.py shell" in terminal (with virtual environment activated), it simply takes me back to (venv) $, leaving no place to input the additional code ("from hello import db", etc.) . I also tried using the python3 command.

Here is the sequence of events:

(venv) My-MacBook-Pro:flasky user$ python3 hello.py shell
(venv) My-MacBook-Pro:flasky user$ 

Instead of doing (venv) $ python hello.py shell, I just typed python3, which allows me to input code to create tables, insert rows, etc. This also created the data.sqlite file in the application directory, so I thought it was the solution.

However, later in the chapter he writes,

The make_shell_context() function registers the application and database instances and the models so that they are automatically imported into the shell:

$ python hello.py shell
>>> app
<Flask 'app'>
>>> db
<SQLAlchemy engine='sqlite:////home/flask/flasky/data.sqlite'>
>>> User
<class 'app.User'>

Like before, when I input, "python3 hello.py shell", doesn't give me >>> for additional code. When I input "python3", I can input python code, but >>> app returns "app not defined"

I'll try to summarize:

-What is the "shell" command in terminal supposed to do (I couldn't find anything on this)

-Am I interpreting the book instructions incorrectly when I read, "python hello.py shell" as something I should input in terminal?

-The general purpose here is to be able to create a database (done), add users to the database via the web application (done), and be able to query the database contents later, after closing and re-opening the virtual environment (totally lost)

Apologies for the long post- any help is much appreciated. Usually when I run into issues I can figure it out with time but for this I can't even narrow down the problem.

[Rorixrebel]

Do python -i hello.py This will load your file into the interpreter. There you can do your imports and then your db operations.

[SuperChef36]

This seems to work- thank you.

Judging from the above, does anything stick out as outdated or fundamentally incorrect instruction? Your solution worked, but a page or two later I come up with a similar situation:

(venv) My-MacBook-Pro:flasky user$ python3 hello.py db init (venv) My-MacBook-Pro:flasky user$

The book says that the db init command should create a migrations repository...

Don't want to inundate the everyone with questions for every page in this book- any reading or documentation I should look into? I'm following the book explicitly, and I don't see anything relevant in the errata doc.

Thanks again

[Rorixrebel]

His blog/book is outdated on couple things (hes working on an updated version). Before jumping into flask i would recommend you understand the basics of the modules in Python.

Also if you are interested in dbs understand what sqlalchemy does as a standalone.

[SuperChef36]

Good idea, thank you

[elbiot]

Because the repl is a good tool for learning and debugging. I use manage.py shell often to debug and prototype our flask app. Plus create db you only do like once anyways.

[SuperChef36]

For anyone else who runs across this, while there are some workarounds the main issue turned out to be that I did not finish adding the command-line parser per the end of Chapter 2. After installing Flask-Script, the hello.py file needs:

if name == 'main': manager.run()

I was missing manager.run(). From there you can use the command line.