monads-py

Python-flavored Option[T] and Result[T, E], empowered with static typing.

features

monads.option:

• Option[T] = Some[T] | Null
• support for match statement:

  match option:
      case Some(value):
          print(value)
  
      case Null.null:
          ...

monads.result:

• Result[T, E] = Ok[T] | Err[E]
• support for match statement:

  match result:
      case Ok(value):
          print(value)
  
      case Err(err):
          print(err)

monads.tools:

• from_none turns T | None into Option[T]:

  data: dict[str, int] = {}
  value: Option[int] = from_none(data.get("foo"))

• try_option turns functions that return T or raise E into Option[T]
• try_result turns functions that return T or raise E into Result[T, E]
• CatchResult captures the result (or exception) of a block of code into Result:

  with CatchResult(OSError) as catch:
      catch @= await client.get("foo")
  
  catch.result  # Ok(data) | Err(OSError(...))

• collect_options collects Iterable[Option[T]] into Some[list[T]] iff all options are Some, else Null
• collect_results collects Iterable[Result[T, E]] into Ok[list[T]] iff all results are Ok, else the first Err[E]