Advanced Usage

Two ways to chain callables with |: build a reusable function lazily, or pipe a value through right away

Function Factory

Bare pipef, never called, builds a reusable function out of everything piped into it

from pipef import pipef

fn_1 = pipef | add_2 | mult_3
fn_1(2)
> 12

Forking

Because every step returns a fresh function, piping more off one never touches the original

from pipef import pipef

fn_1 = pipef | add_2 | mult_3
fn_2 = fn_1 | add_2
fn_3 = fn_1 | minus_3
fn_2(2)
> 14
fn_3(2)
> 9
fn_1(2)
> 12

Immediate Invocation

Calling pipef(...) pipes those arguments through the chain right away, one step at a time

With Args

Each | applies immediately, and the final result unpacks with result, = or a plain call

from pipef import pipef

result, = pipef(2) | add_2 | mult_3
result
> 12
result_fn = pipef(2) | add_2 | mult_3
result, = result_fn
result
> 12
result = result_fn()  # optional behaviour
result
> 12

With Kwargs

The first function in the chain takes keyword arguments too, spread in alongside any positional ones

from pipef import pipef

result, = pipef(1, 2, c=3) | (lambda a, b, c: a + b + c) | add_2
result
> 8

Empty

Even with nothing passed in, piping still works — the first function is just called with no arguments

from pipef import pipef

result, = pipef() | (lambda: 1) | add_2
result
> 3

Forking

Piping further off an already-resolved result forks a new one without changing it

from pipef import pipef

result_fn = pipef(2) | add_2 | mult_3
result_1, = result_fn | add_5
result_1
> 17
result_2, = result_fn | minus_3
result_2
> 9
result_0, = result_fn
result_0
> 12

Edge Cases

Behavior for the boundary inputs above, where a seed holds nothing, or only part of what was passed in

On Its Own

Left as is, with nothing piped in either, an empty pipef() simply holds None

from pipef import pipef

pipef()
> None

Reading Before Piping

Reading a seed before piping only exposes its first positional argument, leaving any other positional or keyword arguments held unused until you pipe them into a function

from pipef import pipef

result, = pipef(1, 2)
result
> 1
result, = pipef(1, x=2)  # x=2 is held but unused here — pipe it into a function to consume it
result
> 1
result, = pipef(x=2)  # a keyword-only seed falls back to None the same way an empty pipef() does
result
> None