iterables.folding

Module pythonic_fp.iterables.folding

pythonic_fp.iterables.folding.accumulate(iterable: Iterable, f: Callable[[L, D], L], initial: L | NoValue = NoValue()) → Iterator

Returns an iterator of partial fold values.

A pure Python version of standard library’s itertools.accumulate

  • function f does not default to addition (for typing flexibility)

  • begins accumulation with an “optional” initial value

Parameters:

  • iterable – iterable to be folded

  • f – two parameter function, first parameter for accumulated value

  • initial – “optional” initial value to start fold

Returns:

an iterator of the intermediate fold values

pythonic_fp.iterables.folding.fold_left(iterable: Iterable, f: Callable[[L, D], L], initial: L) → L | Never

Fold an iterable left with a function and initial value.

  • not restricted to __add__ for the folding function

  • initial value required, does not default to 0 for initial value

  • handles non-numeric data just find

Warning

This function never return if given an infinite iterable.

Warning

This function does not catch any exceptions f may raise.

Parameters:

  • iterable – iterable to be folded

  • f – two parameter function, first parameter for accumulated value

  • initial – mandatory initial value to start fold

Returns:

the folded value

pythonic_fp.iterables.folding.maybe_fold_left(iterable: Iterable, f: Callable[[L, D], L], initial: L | NoValue = NoValue()) → MayBe | Never

Folds an iterable left with an “optional” initial value..

  • when an initial value is not given then L = D

  • if iterable empty and no initial value given, return MayBe()

Warning

This function never return if given an infinite iterable.

Warning

This function returns a MayBe() when f raises any exception what-so-ever. The exception is thrown away.

Parameters:

  • iterable – The iterable to be folded.

  • f – First argument is for the accumulated value.

  • initial – Mandatory initial value to start fold.

Returns:

MayBe of a successfully folded value, otherwise MayBe()

pythonic_fp.iterables.folding.reduce_left(iterable: Iterable, f: Callable[[D, D], D]) → D | Never

Fold an iterable left with a function.

Warning

This function never return if given an infinite iterable.

Warning

This function does not catch or re-raises exceptions from f.

Parameters:

  • iterable – iterable to be reduced (folded)

  • f – two parameter function, first parameter for accumulated value

Returns:

reduced value from the iterable

Raises:

  • StopIteration – when called on an empty iterable

  • Exception – does not catch any exceptions from f

pythonic_fp.iterables.folding.sc_reduce_left(iterable: ~collections.abc.Iterable, f: ~collections.abc.Callable[[D, D], D], start: ~collections.abc.Callable[[D], bool] = <function <lambda>>, stop: ~collections.abc.Callable[[D], bool] = <function <lambda>>, include_start: bool = True, include_stop: bool = True) → tuple[MayBe, Iterator]

Short circuit version of a left reduce.

Useful for infinite iterables.

Behavior for default arguments will

  • left reduce finite iterable

  • start folding immediately

  • continue folding until end (of a possibly infinite iterable)

Parameters:

  • iterable – iterable to be reduced from the left

  • f – two parameter function, first parameter for accumulated value

  • start – delay starting the fold until it returns true

  • stop – prematurely stop the fold when it returns true

  • include_start – if true, include fold starting value in fold

  • include_stop – if true, include stopping value in fold

Returns:

tuple of a MayBe of the folded value and iterator of remaining iterables

pythonic_fp.iterables.folding.sc_reduce_right(iterable: ~collections.abc.Iterable, f: ~collections.abc.Callable[[D, D], D], start: ~collections.abc.Callable[[D], bool] = <function <lambda>>, stop: ~collections.abc.Callable[[D], bool] = <function <lambda>>, include_start: bool = True, include_stop: bool = True) → tuple[MayBe, Iterator]

Short circuit version of a right reduce.

Useful for infinite and non-reversible iterables.

Behavior for default arguments will

  • right reduce finite iterable

  • start folding at end (of a possibly infinite iterable)

  • continue reducing right until beginning

Parameters:

  • iterable – iterable to be reduced from the right

  • f – two parameter function, second parameter for accumulated value

  • start – delay starting the fold until it returns true

  • stop – prematurely stop the fold when it returns true

  • include_start – if true, include fold starting value in fold

  • include_stop – if true, include stopping value in fold

Returns:

tuple of a MayBe of the folded value and iterator of remaining iterables