Programmer blog

One comes to a task that has to do with counting items in a database. We will describe the right approach here. Despite being so obvious I did not find much of the docs for junior developers to watch and learn. Here is a sample task and solution: Let's assume we have a model like so: class Cycle (db.Model): id = db.Column(db.Integer, primary_key= True ) object_id = db.Column(db.String, nullable= False ) Sample date populated into it will be: { id : 1 , object_id: 'unique1' }, { id : 2 , object_id: 'unique1' }, { id : 3 , object_id: 'unique2' }, { id : 4 , object_id: 'unique2' }, { id : 5 , object_id: 'unique2' }, { id : 6 , object_id: 'unique3' } We need to count unique model instances with same  object_id . To achieve this relatively simple task one would go straightforward. E.g. Fetch all the Cycle instances with a simple query and then...

Despite using console most of the time I have a preference to edit PostgreSQL databases through UI. Especially when it comes to remote side. Usually one can access this through  $ psql  command. However this tends to writing raw SQL queries and a lot of typing in overall. Here is a way to do it with UI. First one needs to make a tunnel.Command is fairly simple: ssh - fNg - L 5555 : localhost : 5432 { username } @ { host . com } One has a tunnel afterwards. This command opens a SSH connection in the background mapping your local port 5555 to your server’s port 5432 (Postgres’ default port). To understand one can observe the meaning of the flags via  $ man ssh  to see what each of these flags doing.  It can be accessed via localhost tools like pgAdmin4 at localhost and port 5555 DB config would look like so:

I have gotten to setting UP a Flask environment for a project recently. Was completely puzzled by how to run this. I have used to running Django project with python manage.py script. This means pointing out a PyCharm interpreter into a certain point of entry, that is also a .py file also. In flask way of starting things there is another approach however. Here it is in Flask Docs. It states to set a variable FLASK_APP and then run a flask run command. This will confuse running a python script way of a project being run. Thus to fix this one needs to set a path to flask binary file. It usually is within a virtual environment binary directory, place where your python interpreter resides. So to set debugging one needs to set path to script binary one needs: Script: /path/to/env/bin/flask Script parameters: run   Environment variable  FLASK_APP=app.py Environment variable FLASK_DEBUG=True Set working directory back to your app path (It changes automatically according t...

Found a new pattern to use recently that is called Promise. I really like the way ES6/7 brings new thinking patterns into life nowdays. Here is Promise used instead of old pattern. It was to give JS method a callback function. This splitting code and making a lot of possibilities for error to come out in this place. One would write old times according to MDN : function greeting ( name ) { alert ( 'Hello ' + name ); } function processUserInput ( callback ) { var name = prompt ( 'Please enter your name.' ); callback ( name ); } processUserInput ( greeting ); And now it is made with Promise pattern like so: let promise = new Promise (( resolve , reject ) => { resolve ( prompt ( 'Please enter your name.' )); }); promise . then (( name ) => { alert ( 'Hello ' + name ); }); In general and briefly this now helps to avoid 'callback hell' with functions passed as arguments and write as...