Something may have gone wrong with thet new vm's install. Or there is some important package missing. I noticed also that in the new vm's xfce terminal, there is no colours with output of "ls".

That's not weird when using root-account. But using a normal user account...

Anyways, changed logging settings in postgres-container. I started getting "LOG connection authetticated"-messages.
Entered into running python container with docker exec, started Python interpreter and started entering commands. Those "authenticated"-messages arrived into stderr. So now i know that sqlalchemy can connect into  postgres.

But "r=conn.execute(text("SELECT * FROM table1"))", which i tried instead of "c.select().where()" is still a problem. For some reason it doesn't return any rows. I think it should.
And it is very stupid if i have to enter commands that way.   I thought that with sqlalchemy, another way of doing queries would be possible.

But i'm not sure that those commands end up in postgres-container. So i'll have to tail -f some_log_file . Postres-container should echo some parts of the commands it receives, into stdout. And i haven't noticed any from that Flask-container.

Another thing is commands trying to select from database pg_catalog. I know these are necessary in order to copy pre-existing database structure into code. 
The account i use to select from "table1" may not have necessary privileges to use that catalog. Have to do some gogling to find out which are the absolute minimal grants that i need.
IMO it is stupid to GRANT ALL PRIVILEGES ON ALL DATABASES just to select from 1 table.

But anyways, working example code would be very nice to find.
It was 2012 when i tried Flask before. I have the previous "hello_world"-attempt printed in paper. But it is half-finished and outdated. And then there is the principal problem that i don't need to define all the tables in code when i have already built the db, outside the Flask-container.

P.S. and then there is the question about psycopg2, which version actually works and can i download it from anywhere anymore? And is "no news is good news" still a valid principle?

(This is Devuan-related in the sense that the host OS is Devuan Chimaera. Inside and outside the vm. ')

First time in 10 years i try to write a simple app with Flask and SQLAlchemy. Should be a simple thing, but more the instructions i read, the more confused i become. A three day parade march to Kabul is turning into a 10-year-long-nightmare-in-the-mountains.

I mean, it should't bee too difficult to:

1. set up connection to a pre-existing db
2. query a table with user-provided value
3. show result back to user somehow

But i have been running into many kinds of errors today.

I think setting up the conn works

e=sqlalchemy.create_engine(<A_CONNECTION_STRING>, echo=True)
conn=e.connect()

at least i get no complaints from Flask.
I query the table with:

metadata=MetaData()
c=Table('table1', metadata, autoload_with=e)
q=c.select().where(c.id_field==user_provided_id)
res=conn.execute(q).fetchone()

... and couldn't get to phase #3 . There were all kinds of complaints. For example:"AttributeError 'Table' object has no attribute 'id_field' ".

I have confirmed, with psql that i can connect to the db with the connectionstring(to be more precise:login, password and other params) i have. Also i have confirmed that  name of the table and column are right. There also should be row with the id value i tried with.

Any working example code anaywhere which does what i'm looking for?
I mean i have read some of the sqlalchemy docs. Also tried https://www.datacamp.com/tutorial/sqlal … l-examples and https://www.blog.pythonlibrary.org/2010 … databases/ . To no avail.

One thing that can complicate simple things is Docker. I use bitnami/python:3.8.17. Tried also bitnami/python:latest. No difference, the Flask app is still not working.

Nothing surprising in Dockerfile: WORKDIR , COPY requirements.txt into container and RUN pip -r requirements.txt . And outside of Dockerfile, mount the app directory.

Inside vm, "dpkg -l docker*" says:

ii docker-compose 1.25.0-1
ii docker.io 20.10.5+dfsg10+deb11u2

And requirements.txt pip uses says, amongst other things:

Flask==3.0.0
psycopg2-binary==2.9.9
SQLAlchemy==2.0.22

There were also line: "flask-sqlalchemy==3.1.1". But i commented that out. To see if something changes. Nope. Not in a way that matters.

I suspect that those packages installed by pip also complicate a task that should be simple. New version of every package comes out 2 or 3 times a day and no one bothers to check if they work as intended or not. Which versions should work? Should i comment out flask-sqlalchemy or SQLAlchemy? Commenting out both will definitely prevent the db connection.

Somehow i'm not surprised that SQL injection is still a thing in 2020'ies. It seems that devs are forced to do queries in a very primitive and dangerous way.
Also it seems that it is mandatory to use scripting language abominations from the 1990'ies to get anything done at all.