pyfunctional

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This is a collection of functional tools I like to use in Python

Contents

def alleq(iterable: Iterable[S]) -> bool

returns True if an iterable is empty or if all elements are equal to the first

def transpose(double_iterable: Iterable[Iterable[S]])

an iterable object that takes a nested iterable and transposes it lazily

def repeat(element: E, count: int)

an iterable object that takes an element and a count and returns that element count times

def attempt(
  block: Callable[[Any], T],
  default: T = None,
  catch: Union[Type[Exception], Iterable[Type[Exception]]] = (Exception,),
  args: Iterable[Any],
  kwargs: Dict[Any, Any]
) -> T

a function that takes a callable, a default value, a list of excpetion types, an arg tuple, and a kwarg dict and calls the callable, catching the exceptions specified, and returning the function value on success, the default value on a known caught exception, and allowing any other none-accounted for exceptions bubble up.

def rreduce(
    reduction: Callable[[R, E], R],
    indexable: Indexable,
    initvalue: Union[R, Sentinel] = sentinel
) -> R

Performs the same operation as functools.reduce but working from the right side (high indices) of the collection rather than the start (lower indices) of the collection. Requires the collection to support len() and indexing (iterators do not support __getitem__ but lists and tuples--for example--do)

Not the specification for Indexable below

from typing import Protocol

class Indexable(Protocol):
  def __getitem__(self, index: int) -> Any: ...
  def __len__(self) -> int: ...

def commute(fn: Callable[[S, T], R]) -> Callable[[T, S], R]

Commutes the operands of a binary function. Does not (yet) work for varargs or functions other than 2-arity

def identity(x: T) -> T

The identity function

def bind(fn: Callable[[Any], R], arg: Any, position: int = 0) -> Callable[[Any], R]

Given a n-arity function fn, bind arg to the positionth argument of fn and return a new function which takes n-1 args. The new function behaves as if the positional argument at posititon was removed from the argument order.

The argument count is 0 based

If fn.__code__.co_argcount is less or equal to posititon the function will raise a ValueError

def full(fn: Callable[[Any], R], *args: Any) -> Callable[[], R]

Like functools.partial, except requires you to fill in all the arguments of fn. Returns a new function that passes *args to fn but takes no arguments itself and returns the return value of fn