#213: Uh oh, Vulcans have infiltrated Flask

Published Wed, Dec 23, 2020, recorded Wed, Dec 23, 2020

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Special guest: Anthony Shaw

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Michael #1: Django Ledger Project

by Miguel Sanda
The mission is to provide free and open source accounting software that could easily replace commercial alternatives like QuickBooks.
Django Ledger supports:
- Chart of Accounts.
- Financial Statements (Income Statement & Balance Sheets).
- Automatic financial ratio & insight calculations.
- Multi tenancy.
- Hierarchical entity management.
- Self-contained Ledgers, Journal Entries & Transactions.
- Financial Activities Support (operational/financial/investing).
- Basic OFX & QFX file import.
- Bills & Invoices with optional progressible functionality.
- Basic navigational templates.
- Entity administration & entity manager support.
- Bank Accounts.
Not quite ready for production.
This project is actively looking for contributors. Any financial and/or accounting experience is a big plus. If you have prior accounting experience and want to contribute, don't hesitate to contact.
Browse the screenshots on the github repo.

Brian #2: Flask-Meld: simple JavaScript interactive features without all of the JavaScript.

Flask-Meld article with example
- Michael Abrahamsen, @MikeAbrahamsen
- working example, code for example
- It seems really zippy. Definitely gonna try this.
Similar project for Django: django-unicorn
- Adam Hill, @adamghill
- todo example

Anthony #3: Bitwise operators in Python (RealPython)

Article by Bartosz Zaczyński

Particularly useful for the enum.IntFlag and enum.Flag classes in the stdlib since 3.7

    >>> class Color(Flag):
    ...     RED = auto()
    ...     BLUE = auto()
    ...     GREEN = auto()
    ...     WHITE = RED | BLUE | GREEN

Michael #4: Why should you use an ORM (Object Relational Mapper)?

You may have heard you should use an ORM, but why?
To get a better understanding of how ORMs work, it’s helpful to work through the kind of problems they can solve.
Data modeled as classes is great but has some shortcomings
- How do you query, filter, sort it?
- How do you store it? Classes live in memory only and pickling isn’t ideal for many reasons
- There is also concurrency, transactional operations/atomiticity
Enter the DB
- But plain SQL is error prone (did you refactor that name? oops)
- Plain SQL has code written within another language (SQL within Python, tools help but still)
- Plain SQL has potential security issues (unless you use parameters)
ORMs
- ORMs are libraries that sit between the SQL database world and your object-oriented programming language world.
- For all intents and purposes, they are an abstraction layer that allows, among other things, for the translation of Python to SQL.
A cycle is formed
- Define our models in the Python world as objects
- the ORM layer translates those models to SQL statements with SQL types to create tables and columns.
- In our application, we instantiate objects from those models, which creates rows in the aforementioned tables.
- Finally, when we want those objects back, we use Python code to retrieve them, which triggers the ORM layer to create the necessary query to retrieve the rows from the database. Then, the ORM layer takes the resulting rows and maps them back to objects.
And you get migrations

Brian #5: sqlite-utils: a Python library and CLI tool for building SQLite databases

Simon Willison, @simonw
“sqlite-utils is a combination Python library and command-line tool I’ve been building over the past six months which aims to make creating new SQLite databases as quick and easy as possible.”
CLI for sqlite
- Run queries and output JSON, CSV, or tables
- analyzing tables
- inserting data
- creating, dropping, transforming tables
- creating indexes
- searching
- …

Python API for using as a library

way easier interaction with sqlite.

    import sqlite_utils
    db = sqlite_utils.Database("demo_database.db")
    # This line creates a "dogs" table if one does not already exist:
    db["dogs"].insert_all([
        {"id": 1, "age": 4, "name": "Cleo"},
        {"id": 2, "age": 2, "name": "Pancakes"}
    ], pk="id")

sqlite-utils docs

Anthony #6: Online conferences are not working for me. But this was a good talk,

“What the struct?!” by Zachary Anglin at the Pyjamas conference.
Explains the struct libraries macro-language for converting binary data structures into Python native types (and vice versa) https://docs.python.org/3/library/struct.html#format-characters
Really nice if you want to programmatically edit/read binary structure (combining with the bitwise operators).
If you’re getting into this topic. Save-game hacking is an interesting place to start.
I use SynalizeIT! /Synalysis as a binary data grammar explorer. It has some example save game formats https://www.synalysis.net/formats.xml
Its also great for hacking/CTF.

https://youtu.be/QT_NAk_peHQ?t=7130

Extras

Brian: