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

Published Tues, Dec 3, 2019, recorded Tues, Nov 26, 2019.

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

  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:

Joke

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

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