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pydantic-linq

C# LINQ for Python. It has every System.Linq and System.Linq.Async operator, is fully typed, and works with Pydantic models.

pip install pydantic-linq

from pydantic import BaseModel
import pydantic_linq  # adds LINQ operators to list / tuple / set / frozenset

class Row(BaseModel):
    id: int
    tag: str

rows = [Row(id=1, tag="a"), Row(id=2, tag="b"), Row(id=3, tag="a")]

rows.where(lambda r: r.tag == "a").select(lambda r: r.id).to_list()         # [1, 3]
rows.group_by(lambda r: r.tag).select(lambda g: (g.key, g.count())).to_list()  # [('a', 2), ('b', 1)]

Why

  • The same API as C#. The names are the C# names in snake_case: OrderByDescending becomes order_by_descending. The overloads and the error behavior match the C# ones. See the operator map.
  • Deferred and re-enumerable. A query does nothing until you enumerate it, and you can enumerate it again, as in .NET.
  • Typed. Generics flow through every operator, so rows.select(lambda r: r.id) is an Enumerable[int] to pyright and mypy.
  • Pydantic-aware. cast(Model) validates raw dicts. Enumerable[Model] works as a field type. The set operators compare models by value. See Pydantic.
  • Entity Framework too. pydantic_linq.orm runs the same LINQ as SQL through SQLModel, with DbContext, include, execute_update and the *_async operators. See Entity Framework.
  • Async too. AsyncEnumerable takes sync or async sources and sync or async selectors. See Async.

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