decorator_experiments.py

import functools
import random


def once_only(f):
    """A function decorater that ensures the decorated function is only called
    once during the lifetime of the VM."""
    static_data = dict(been_called=False, result=None)

    @functools.wraps(f)
    def wrapper(*args, **kwargs):
        if not static_data["been_called"]:
            static_data["result"] = f(*args, **kwargs)
            static_data["been_called"] = True
            return static_data["result"]

    return wrapper


class DependencyNotFoundError(NameError):
    pass


def depends(dependency_list):
    """A function decorator that  ensures that the depended-upon functions are
    called (in order) before the decorated function is called. Dependencies
    will be called without any arguments."""

    def decorator(f):
        @functools.wraps(f)
        def wrapper(*args, **kwargs):
            for dependency in dependency_list:
                if callable(dependency):
                    dependency()
                else:
                    if dependency in globals():
                        globals()[dependency]()
                    else:
                        raise DependencyNotFoundError(
                            "Dependency not found: %s" % dependency
                        )
            return f(*args, **kwargs)

        return wrapper

    return decorator


def krisskross(fn):
    """
    Well make you jump, jump (out of a window)
    50% chance of reversing the order of args and kwargs keys
    """

    def wrapped(*args, **kwargs):
        if random.choice([True, False]):
            return fn(*args[::-1], **{k[::-1]: v for k, v in kwargs.items()})
        return fn(*args, **kwargs)

    return wrapped


@once_only
def should_only_run_once():
    print("Function has been run!")


should_only_run_once()
should_only_run_once()


def a1():
    print("a1")


def b1():
    print("b1")


@depends([a1, b1])
def c1():
    print("c1")


print("--------")
c1()


@depends([a1])
def b2():
    print("b2")


@depends([b2])
def c2():
    print("c2")


print("--------")
c2()


@depends(["a1", "b1"])
def c3():
    print("c3")


print("--------")
c3()


@krisskross
def guess_the_order(*args, **kwargs):
    print(args)
    print(kwargs)


guess_the_order(1, 2, 3, hello="world")
guess_the_order(1, 2, 3, hello="world")
guess_the_order(1, 2, 3, hello="world")
guess_the_order(1, 2, 3, hello="world")