Little λ

Little λ is a tiny python utility for function composition!

Little λ supports a functional-like syntax for function composition by extending the @ operator used for linear function composition to nonlinear functions.

To use, simply put a little λ at the start of the functions you want to compose separated by composition operators @:

n_unique = λ @ len @ set
n_unique([1, 1, 4, 5])
# returns 3

The λ can also be used to generate simple lambda functions from most binary operations, which can themselves be composed:

is_even = (λ == 0) @ (λ % 2)

Note that the term (λ == 0) counts as a λ at the start of the composition.

Finally, Little λ can be used for partial application via λ(fn, *args, **kwargs). This makes it particularly easy to use λ with higher-order functions:

sum_of_squares = λ @ sum @ λ(map, λ ** 2)

Here, λ(map, λ ** 2) is the map function, partially applied with the square function.

Little λ makes your functional Python code look the part!

sum_of_even_squares = λ @ sum @ λ(map, λ ** 2) @ λ(filter, (λ == 0) @ (λ % 2))

WARNING

Little λ is not a maintained package and is not intended for serious use. It is by design not Pythonic, and it likely has many edge-cases I'm unaware of, and may not ever fix.