Python: Uncovering the Overlooked Core Functionalities

Re:Python: Uncovering the Overlooked Core Functionalities by qsort on Monday July 24, 2023 @04:54PM (#36854064)

Just to clarify, I don't mean your article is bad or incomplete -- quite the contrary, I enjoyed it a lot. Generators are one of my favorite Python features and they're kind of underused, mostly because people simply don't know about them.

A couple more along the same lines:

- Metaclasses and type. (This is admittedly dark magic, but useful in library code, less so in application code)

- Magic methods! Everyone knows about __init__, but you can override all sorts of behaviors (see: https://docs.python.org/3/reference/datamodel.html)

My favorite example (I have a lot of favorite examples :)) is __call__, which emulates function calling and is the equivalent of C++'s operator().

Why is it my favorite? Because as the old adage goes, "a class is a poor man's closure, a closure is a poor man's class":

  class C:
      def __init__(self, x):
          self.x = x
      def __call__(self, y):
          return self.x + y
 
  >>> a = C(2)
  >>> a(3)
  5

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Re:Python: Uncovering the Overlooked Core Functionalities by erikvdven on Monday July 24, 2023 @05:16PM (#36854303)

Thanks a lot! Really appreciate it. Love the example! Haven't used the dunder __call__ yet (like many magic methods I guess), but that's a nice one!

I didn't have to use Metaclasses, either, though I have read about them, especially in Fluent Python. But I guess I belong to the 99% who haven't had to worry about them, yet :P

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Re:Python: Uncovering the Overlooked Core Functionalities by learplant on Monday July 24, 2023 @08:51PM (#36856340)

I find that __call__ is very confusing, but maybe because I'm not used to seeing if often.

What is the benefit compared to having a method named "add" that also explains the behavior?

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Re:Python: Uncovering the Overlooked Core Functionalities by Jtsummers on Monday July 24, 2023 @08:58PM (#36856408)

If an object is callable you can use it in places that might conventionally expect functions. The utility of that is very situational, though. I've only used it a handful of times myself over the years I've known and used Python.

It may also give you a "clearer" (in quotes because subjective) presentation for something you're trying to do.

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Re:Python: Uncovering the Overlooked Core Functionalities by claytonjy on Monday July 24, 2023 @10:21PM (#36857078)

I see it a lot in HuggingFace, and use it myself for classes that are used like a function, especially when the obvious method name is the verb form of the class name

    processor = SomeProcessor.load("path/to/config")

    # with __call__
    processed_inputs = processor(inputs)

    # less awkward than
    processes_inputs = processor.process(inputs)

The only benefit is to the human, same as @property or even @dataclass.

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Re:Python: Uncovering the Overlooked Core Functionalities by learplant on Tuesday July 25, 2023 @05:51PM (#36870089)

Thanks for writing that up! I disagree though, I prefer the processor.process for clarity, and for not adding another way of doing things that regular methods already do.

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