conditional_dispatch

Simple little decorator to create generic functions with conditional dispatching. This is useful for breaking up a single function into multiple implementations based on different conditions, without having to write a bunch of if-elif-else statements. I hate those. You can also use it to implement a multiple-argument type dispatcher, which is pretty cool. Feel free to copy/paste in your own projects! Uses syntax like python's standard library's singledispatch and is able to be used with class and instance methods.

Examples

"""
Example of variable argument dispatch
"""

@conditional_dispatch
def my_function(*args: Any) -> None
  ...

@my_function.register(lambda *args: len(args) == 0)
def _(*args) -> None:
  print("One argument")

@my_function.register(lambda *args: len(args) > 0)
def _(*args) -> None:
  print("Multiple arguments")

"""
Example of multiple type dispatch
"""

@conditional_dispatch
def my_function(a: Any, b: Any) -> str:
  raise TypeError(f"Dispatching error: no support for {type(input)}")


@my_function.register(lambda a, b: isinstance(a, int) and isinstance(b, int))
def _(a: int, b: int) -> str:
  return "Both are ints"


@my_function.register(lambda a, b: isinstance(a, int) and a >= 0 and isinstance(b, str))
def _(a: int, b: int) -> str:
  return "a is an int and b is str"


@my_function.register(lambda a, b: isinstance(a, str) and isinstance(b, int))
def _(a: str, b: int) -> str:
  return "a is a str, b is an int"

@my_function.register(lambda a, b: isinstance(a, str) and isinstance(b, str))
def _(a: str, b: str) -> str:
  return "Both are strs"