Tuesday, March 27, 2018

Functional Python Programming 2e -- Now With Type Hints

Functional Python Programming, 2nd ed.

This has been fun to cleanup some rambling, reset the math to be sure it's actually right.

And.

Type Hints.

Almost every example has had type hints added.

(And I raised the pylint scores be rearranging some spacing and what-not.)

Bonus. We will be moving the publication date up from June to possibly April. We're still doing technical reviews and what-not, so things aren't *done*.

What was hardest?

Generics, specifically, decorators can have quite complex type hints. Indeed, type hinting raises important questions about trying to write super-generic functions that can handle too wide a spectrum of types.

def some_function(arg):
    if isinstance(arg, dict):
        do_something(arg)
    elif isinstance(arg, list):
        do_something({i: v for i, v in enumerate(arg)})
    else: 
        do_something(dict(arg=arg))


This kind of thing turns out to be ill-advised. It's probably a bad design. More importantly, it's difficult to annotate, making it difficult to discern if it behaves correctly.

In this case, the argument is Union[Dict, Sequence, Any]. I've got a few examples of Union types, but they're rare because I'm not a fan in the first place. And the few places I used them, the complexity of getting past mypy type checks showed that they add risk and cost without a dramatic reduction in complexity.

In this specific case, the some_function() function is merely a type-converting wrapper around the do_something() function. It's probably better to refactor the type conversion responsibility into the clients of some_function().

The arguments about "encapsulation" or "the client shouldn't know that detail" are generally kind of silly. We're all adults here, we generally have to know what's going on with respect to the conversions in order to use the function correctly and write unit tests.

Tuesday, March 20, 2018

HATEOAS is useless? Or not used enough?

See Why HATEOAS is useless and what that means for REST.

The article provides a background leading up to these observations:
  • There are very few good tools to create a REST API using this style
  • There are no clients widely used to consume these types of APIs
The "useless" in the title is more like "not used enough."

There's a multi-part conclusion that may be more helpful if it's fleshed out further. For now, however, it appears that the big problems center around:
  • You still need to write Open Api Specifications (OAS, f/k/a Swagger). I don't think this is bad. The blog post makes it sound like a problem. I think it's essential.
  • You need to put versioning somewhere. The path is less than idea. I'm big on the Accept header containing application-specific MIME types. For example, application/vnd.com.your-name-here.app.json+v1. This doesn't strike me as a problem, either.
  • The whole approach is "closer to RPC than some REST lovers like to admit." I think this point revolves around the way JSON-RPC or SOAP involves some overheads above basic HTTP that are unhelpful. I don't think the "closer to RPC" follows logically from the lack of tooling for HATEOS, but it certainly could be true that a badly-done API might involve too many of the wrong kinds of overheads.
I think there's a hidden strawman here. The "automatic discovery" idea. I don't think this idea makes a lick of sense. Some people think it's implied (or required) by REST, and any failure to provide for fully-automated semantically rich discovery of an API is some kind of failure.

I don't think full semantic discovery is possible or even desirable. 
  • It's not possible because of the problem of assigning names and meanings to resources and verbs in an end-point. The necessary details can only be exposed with a semantically complete ontology and complex SPARQL queries into the ontology to find resources and end-points. 
  • It's not desirable because we replace a human-focused OAS with a complete ontology that has to be rigorously defined, and tested to be sure that all kinds of automated discovery algorithms can understand the provided details. And none of this addresses the actual application, it's all rich, detailed meta-description of the application.
I don't see why we're trying to replace people. API discovery is actually kind of hard. The resources, their relationships, and the verbs for getting or updating those resources involves an essentially difficult knowledge capture and dissemination problem. 

Friday, March 9, 2018

Python Interviews

The #Python Interviews book is out. Mike Driscoll interviewed a bunch of Python experts. And me, too. get 30% off the Amazon paperback version of the book using the code 30PYTHONhttps://goo.gl/5A3uhq

Here's a flavor of how this went:

Driscoll: So how did you end up becoming an author of Python books?
Lott: Most roles in my career more or less just happened to me, but becoming a writer was a conscious decision.
In this case, I had decided that there could be value in teaching the Python language and the associated software engineering skills. I started to collect notes for a book in 2002. By 2010, I had tried self-publishing several books on Python.
When Stack Overflow started, I was an early participant. There were many interesting Python questions. The questions showed gaps where more information was needed about Python specifically and software engineering in general. Over a few years, I answered thousands of questions about Python and somehow built up a large reputation.

Monday, March 5, 2018

Python Interviews -- Coming Soon from Packt

See https://www.packtpub.com/web-development/python-interviews

I'm honored.

I'll be studying what the other folks have to say in here. Being in the Python community means respecting other's views. And that means understanding them.

This looks like fun because it isn't *deeply* technical, it's about people and technology.