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A typesafe list with more method chaining!

Project description

Slist

This is a drop in replacement for the built-in mutable python list

But with more post-fixed methods for chaining in a typesafe manner!!

Leverage the latest mypy features to spot errors during coding.

All these methods return a new list. They do not mutate the original list.

Not able to convince your colleagues to use immutable functional data structures? I understand.
This library lets you still have the benefits of typesafe chaining methods while letting your colleagues have their mutable lists!

pypi python Build Status

pip install slist

Quick Start

Easily spot errors when you call the wrong methods on your sequence with mypy.

from slist import Slist

many_strings = Slist(["Lucy, Damion, Jon"])  # Slist[str]
many_strings.sum()  # Mypy errors with 'Invalid self argument'. You can't sum a sequence of strings!

many_nums = Slist([1, 1.2])
assert many_nums.sum() == 2.2  # ok!

class CannotSortMe:
    def __init__(self, value: int):
        self.value: int = value

stuff = Slist([CannotSortMe(value=1), CannotSortMe(value=1)])
stuff.sort_by(lambda x: x)  # Mypy errors with 'Cannot be "CannotSortMe"'. There isn't a way to sort by the class itself
stuff.sort_by(lambda x: x.value)  # ok! You can sort by the value

Slist([{"i am a dict": "value"}]).distinct_by(
    lambda x: x
)  # Mypy errors with 'Cannot be Dict[str, str]. You can't hash a dict itself

Slist provides methods to easily flatten and infer the types of your data.

from slist import Slist, List
from typing import Optional

test_optional: Slist[Optional[int]] = Slist([-1, 0, 1]).map(
    lambda x: x if x >= 0 else None
)
# Mypy infers slist[int] correctly
test_flattened: Slist[int] = test_optional.flatten_option()


test_nested: Slist[List[str]] = Slist([["bob"], ["dylan", "chan"]])
# Mypy infers slist[str] correctly
test_flattened_str: Slist[str] = test_nested.flatten_list()

There are plenty more methods to explore!

from slist import Slist

result = (
    Slist([1, 2, 3])
    .repeat_until_size_or_raise(20)
    .grouped(2)
    .map(lambda inner_list: inner_list[0] + inner_list[1] if inner_list.length == 2 else inner_list[0])
    .flatten_option()
    .distinct_by(lambda x: x)
    .map(str)
    .reversed()
    .mk_string(sep=",")
)
assert result == "5,4,3"

Project details


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