sain

a dependency-free library which implements a few of Rust's core crates purely in Python. It offers a few of the core Rust features such as Vec<T>, Result<T, E>, Option<T> and more. See the equivalent type section below.

a few std types are implemented. Check the project documentation

Install

You'll need Python 3.10 or higher.

PyPI

pip install sain

Overview

sain provides a variety of the standard library crates. such as Vec<T> and converter interfaces.

from sain import Option, Result, Ok, Err
from sain.collections import Vec
from sain.collections.buf import Bytes
from sain.convert import Into, TryFrom

from dataclasses import dataclass, field


# some blob of data.
@dataclass
class Blob(Into[Bytes], TryFrom[str, None]):
    tag: str
    buffer: bytes

    # converts this layout into some raw bytes.
    def into(self) -> Bytes:
        buf = Bytes()
        buf.put_bytes(self.tag.encode())
        buf.put_bytes(b"-")
        buf.put_bytes(self.buffer)
        return buf

    @classmethod
    def try_from(cls, value: str) -> Result[Blob, None]:
        # implement a conversion from a string to a blob.
        # in case of success, return Ok(layout)
        # and in case of failure, return Ok(None)
        tag, buffer = value.split(".")  # this is an example.
        return Ok(Blob(tag, buffer.encode()))


@dataclass
class BlobStore:
    buf: Vec[Blob] = field(default_factory=Vec)

    # extends the vec from an iterable.
    def add(self, *blobs: Blob):
        self.buf.extend(blobs)

    # finds blob that's tagged with `pattern`
    def find(self, pattern: str) -> Option[Blob]:
        return self.buf.iter().find(lambda blob: pattern in blob.tag)

    # converts the entire buffer into `Bytes`
    def into_bytes(self) -> Result[Bytes, None]:
        if not self.buf:
            return Err(None)

        buffer = Bytes()
        for blob in self.buf:
            buffer.put_bytes(blob.into())

        return Ok(buffer)


blobstore = BlobStore()
blobstore.add(Blob("safe", b"Rust"))
# try to convert the string into a Layout.
match Blob.try_from("unsafe.Python"):
    case Ok(blob):
        blobstore.add(blob)  # add it if parsed.
    case Err(_):
        ...  # Error parsing the str.

print(blobstore.into_bytes().expect("cannot convert to bytes").to_str())

built-in types

name in Rust	name in Python	note	restrictions
Option<T>, Some(T), None	Option[T], Some(T), Some(None)	Some(None) has the same layout as None in Rust
Result<T, E>, Ok(T), Err(E)	Result[T, E], Ok(T), Err(E)
Vec<T>	Vec[T]
HashMap<K, V>	HashMap[K, V]
bytes::Bytes	Bytes
LazyLock<T>	Lazy[T]
OnceLock<T>	Once[T]
Box<T>	Box[T]	this isn't a heap box, See
MaybeUninit<T>	MaybeUninit[T]	they serve the same purpose, but slightly different
&dyn Default	Default[T]
&dyn Error	Error
&dyn Iterator<T>	Iterator[T]
Iter<'a, T>	Iter[T]	collections called by .iter() are built from this type
iter::once::<T>()	iter.once[T]
iter::empty::<T>()	iter.empty[T]
iter::repeat::<T>()	iter.repeat[T]
cfg!()	cfg()	runtime cfg, not all predictions are supported
#[cfg_attr]	@cfg_attr()	runtime cfg, not all predictions are supported
#[doc]	@doc()	the docs get generated at runtime
todo!()	todo()
#[deprecated]	@deprecated()	will get removed when it get stabilized in warnings in Python 3.13
unimplemented!()	@unimplemented()

Notes

Since Rust is a compiled language, Whatever predict in cfg and cfg_attr returns False will not compile.

But there's no such thing as this in Python, So RuntimeError will be raised and whatever was predicated will not run.