FunctionalPy

Python has implemented map, filter etc. as functions, rather than methods on a sequence. This makes the result harder to read and Iterators less used than they could be. FunctionalPy exists to change that.

You get this 🔥:

Seq([1,2,3])
   .map(lambda x: multiply_by_2(x))
   .filter(lambda x: is_even(x))

Instead of this:

sequence = [1,2,3]
multiplied = [multiply_by_2(x) for x in sequence]
is_even = [x for x in multiplied if is_even(x)]

Or this:

filter(lambda x: is_even(x), map(lambda x: multiply_by_2(x), [1,2,3]))

Install

pip install functionalpy

Usage

from functionalpy import Seq

result = (Seq([1, 2])
            .filter(lambda x: x % 2 == 0)
            .map(lambda x: x * 2)
            .to_list()
)
assert result == [4]

Philosophy

• Make it work: Concise syntax borrowed from Scala, Rust etc.
• Make it right: Fully typed, no exceptions
• Make it fast: Concurrency through .pmap, potentially caching in the future
• Keep it simple: No dependencies

Prior art

FunctionalPy stands on the shoulders of Scala, Rust etc.

Moreover, PyFunctional has existed for 7+ years with a comprehensive feature set. It is performant, with built-in lineage and caching. Unfortunately, this makes typing non-trivial, with a 4+ year ongoing effort to add types.

Contributing

Devcontainer

1. Install Orbstack or Docker Desktop. Make sure to complete the full install process before continuing.
2. If not installed, install VSCode
3. Press this link
4. Complete the setup process
5. Done! Easy as that.

💬 Where to ask questions