Talk Notes: Practicality Beats Purity: The Zen Of Python's Escape Hatch?

I gave the talk Practicality Beats Purity: The Zen of Python’s Escape Hatch as part of PyConline AU 2020, the very online replacement for PyCon AU this year. In that talk, I included a few interesting links code samples which you may be interested in:

Links and code samples

• 20 Pythonic Fec^WTheses by Tim Peters, from comp.lang.python The Way of Python
• Fantastic Blocks and Where to Hide Them, from PyCon AU 2019
• PEP 8
• PEP 318 which introduce decorators

@apply

def apply(transform):

    def __decorator__(using_this):
        return transform(using_this)

    return __decorator__


numbers = [1, 2, 3, 4, 5]

@apply(lambda f: list(map(f, numbers)))
def squares(i):
  return i * i

print(list(squares))

# prints: [1, 4, 9, 16, 25]

Init.java

public class Init {
  public static void main(String[] args) {
    System.out.println("Hello, World!")
  }
}

@switch and @case

__NOT_A_MATCHER__ = object()
__MATCHER_SORT_KEY__ = 0

def switch(cls):

    inst = cls()
    methods = []

    for attr in dir(inst):
        method = getattr(inst, attr)
        matcher = getattr(method, "__matcher__", __NOT_A_MATCHER__)

        if matcher == __NOT_A_MATCHER__:
            continue

        methods.append(method)

    methods.sort(key = lambda i: i.__matcher_sort_key__)

    for method in methods:
        matches = method.__matcher__()
        if matches:
            return method()

    raise ValueError(f"No matcher matches value {test_value}")

def case(matcher):

    def __decorator__(f):
        global __MATCHER_SORT_KEY__

        f.__matcher__ = matcher
        f.__matcher_sort_key__ = __MATCHER_SORT_KEY__
        __MATCHER_SORT_KEY__ += 1
        return f

    return __decorator__



if __name__ == "__main__":
    for i in range(100):

        @switch
        class FizzBuzz:

            @case(lambda: i % 15 == 0)
            def fizzbuzz(self):
                return "fizzbuzz"

            @case(lambda: i % 3 == 0)
            def fizz(self):
                return "fizz"

            @case(lambda: i % 5 == 0)
            def buzz(self):
                return "buzz"

            @case(lambda: True)
            def default(self):
                return "-"

        print(f"{i} {FizzBuzz}")