#159: Brian's PR is merged, the src will flow

Sponsored by DigitalOcean: pythonbytes.fm/digitalocean

Michael #1: Final type

• PEP 591 -- Adding a final qualifier to typing
• This PEP proposes a "final" qualifier to be added to the typing module---in the form of a final decorator and a Final type annotation---to serve three related purposes:
  • Declaring that a method should not be overridden
  • Declaring that a class should not be subclassed
  • Declaring that a variable or attribute should not be reassigned
• Some situations where a final class or method may be useful include:
  • A class wasn’t designed to be subclassed or a method wasn't designed to be overridden. Perhaps it would not work as expected, or be error-prone.
  • Subclassing or overriding would make code harder to understand or maintain. For example, you may want to prevent unnecessarily tight coupling between base classes and subclasses.
  • You want to retain the freedom to arbitrarily change the class implementation in the future, and these changes might break subclasses.

        # Example for a class:
        from typing import final
    
        @final
        class Base:
            ...
    
        class Derived(Base):  # Error: Cannot inherit from final class "Base"
            ...
    

And for a method:

    class Base:
        @final
        def foo(self) -> None:
            ...

    class Derived(Base):
        def foo(self) -> None:  # Error: Cannot override final attribute "foo"
                                # (previously declared in base class "Base")
            ...

• It seems to also mean const

      RATE: Final = 3000
  
  class Base:
  
          DEFAULT_ID: Final = 0
  
      RATE = 300  # Error: can't assign to final attribute
      Base.DEFAULT_ID = 1  # Error: can't override a final attribute
  

Brian #2: flit 2

Michael #3: Pint

• via Andrew Simon
• Physical units and builtin unit conversion to everyday python numbers like floats.
• Receive inputs in different unit systems it can make life difficult to account for that in software.
• Pint handles the unit conversion automatically in a wide array of contexts – Can add 2 meters and 5 inches and get the correct result without any additional work.
• The integration with numpy and pandas are seamless, and it’s made my life so much simpler overall.
• Units and types of measurements
• Think you need this? How about the Mars Climate Orbiter
  • The MCO MIB has determined that the root cause for the loss of the MCO spacecraft was the failure to use metric units in the coding of a ground software file, “Small Forces,” used in trajectory models. Specifically, thruster performance data in English units instead of metric units was used in the software application code titled SM_FORCES (small forces).

Brian #4: 8 great pytest plugins

• Jeff Triplett

Michael #5: 11 new web frameworks

• via LuisCarlos Contreras

1. Sanic [flask like] - a web server and web framework that’s written to go fast. It allows the usage of the async / await syntax added in Python 3.5
2. Starlette [flask like] - A lightweight ASGI framework which is ideal for building high performance asyncio services, designed to be used either as a complete framework, or as an ASGI toolkit.
3. Masonite - A developer centric Python web framework that strives for an actual batteries included developer tool with a lot of out of the box functionality. Craft CLI is the edge here.
4. FastAPI - A modern, high-performance, web framework for building APIs with Python 3.6+ based on standard Python type hints.
5. Responder - Based on Starlette, Responder’s primary concept is to bring the niceties that are brought forth from both Flask and Falcon and unify them into a single framework.
6. Molten - A minimal, extensible, fast and productive framework for building HTTP APIs with Python. Molten can automatically validate requests according to predefined schemas.
7. Japronto - A screaming-fast, scalable, asynchronous Python 3.5+ HTTP toolkit integrated with pipelining HTTP server based on uvloop and picohttpparser.
8. Klein [flask like] - A micro-framework for developing production-ready web services with Python. It is ‘micro’ in that it has an incredibly small API similar to Bottle and Flask.
9. Quart [flask like]- A Python ASGI web microframework. It is intended to provide the easiest way to use asyncio functionality in a web context, especially with existing Flask apps.
10. BlackSheep - An asynchronous web framework to build event based, non-blocking Python web applications. It is inspired by Flask and ASP.NET Core. BlackSheep supports automatic binding of values for request handlers, by type annotation or by conventions.
11. Cyclone - A web server framework that implements the Tornado API as a Twisted protocol. The idea is to bridge Tornado’s elegant and straightforward API to Twisted’s Event-Loop, enabling a vast number of supported protocols.

Brian #6: Raise Better Exceptions in Python

Extras

Michael:

• Naming venvs --prompt
• Another new course coming soon: Python for decision makers and business leaders
• Some random interview over at Real Python: Python Community Interview With Brian Okken

Joke

• via Daniel Pope
• What's a tractor's least favorite programming language? Rust.