ibis-typing

A typed framework for writing Ibis dataframe expressions — with full IDE support, static analysis, and property-based testing.

Ibis is a portable Python dataframe library (DSL) that runs on DuckDB, Polars, Trino, BigQuery, and more. ibis-typing layers a type-safe schema system on top of it, so your transforms carry type information end-to-end.

DBT is a popular SQL transformation framework. **ibis-typing.dbt ** can compile typed Ibis Expressions to DBT SQL for execution in your warehouse, combining the ubiquity of DBT with the expressiveness and benefits of a high-level typed DSL.

Installation

pip install ibis-typing

uv add ibis-typing

After installation, run the type-patch step once to inject typed overloads into your installed ibis package:

python -m ibis_typing.type_patch

Quick start

1. Define input schemas

from attrs import frozen

from ibis_typing import IbisSchema, it


@frozen
class Transaction(IbisSchema):
    date: it.Date = None
    amount: it.Float64 = None
    category: it.String = None

2. Define a typed expression

# my_app.expressions_pkg.monthly_amounts
from attrs import frozen
from collections.abc import Sequence
from ibis_typing import Expression, IbisTable, this, it
from ibis_typing.ibis_extension_method import TableMethod, ValueMethod
from ibis import Table, ir, literal


@frozen
class MonthlyAmounts(Expression):
    @classmethod
    def from_expression(cls, inputs: IbisTable[Transaction]):
        cols = inputs.cols
        table = (
            inputs.table
            @ AggregateByMonth(cols.date, sums=[cols.amount])
            @ it.deferred.filter(this[cols.amount] != literal(0))
        )
        return cls.of(table)


@frozen
class AggregateByMonth(TableMethod):
    date: it.Date
    sums: Sequence[it.Float64]

    def apply(self, table: Table) -> Table:
        return (
            table
            @ it.Select(expr={"month": this[self.date] @ StartOfMonth()})
            @ it.Aggregate(by=["month"], sum=self.sums)
        )


@frozen
class StartOfMonth(ValueMethod[ir.DateValue, ir.DateValue]):
    def apply(self, value: ir.DateValue):
        return value @ it.defer(ir.DateValue).truncate("M")

3. Generate IbisSchema classes for Expression classes

Generate IbisSchema classes for the output of Expression classes, and write them to .py files:

python3 -m ibis_typing.schemagen \
  my_module.expressions_pkg \
  --schema-package my_app.generated.schemas \
  --schema-suffix Schema \
  --write

Resulting files will contain IbisSchema classes like this:

# my_app.generated.schemas.monthly_amounts_schema
from attrs import frozen
from ibis_typing.ibis_types import *

@frozen
class MonthlyAmountsSchema(IbisSchema):
  month: Date = None
  amount: Float64 = None

Update your Expression classes to use the generated IbisSchema for their output schema:

from my_app.generated import schemas

@frozen
class MonthlyAmounts(schemas.MonthlyAmountsSchema, Expression):
    ...

Tip: Create a regression test that checks for unexpected schema changes, and update expected schemas when intentional changes are made:

# my_app.tests.test_generate_schemas
def test_generate_ibis_expression_schema_packages(update_expected):
  expr_schema_pkgs = {
    samples: sample_schemas,
  }

  expr_to_schema_package = {
    expr: schema_pkg
    for expr_pkg, schema_pkg in expr_schema_pkgs.items()
    for expr in schema_writer.list_expressions_in_package(expr_pkg)
  }

  schema_writer.generate_schemas_with_diff_check(
    expr_to_schema_package, update_expected
  )

4. Test with Hypothesis

pytest fixtures are registered automatically — no conftest.py needed.

from hypothesis import given, strategies as st

from ibis_typing import utils
from ibis_typing.hypothesis import strategy_for


@given(transactions=st.lists(strategy_for(Transaction), min_size=1))
def test_monthly_amounts(evaluate_table, transactions):
    reference_output = utils.group_by(transactions, key=lambda t: t.date.replace(day=1))
    monthly_amounts = [
        MonthlyAmounts(month=month, amount=sum(t.amount for t in month_transactions))
        for month, month_transactions in reference_output.items()
    ]

    # Get evaluated expression rows together with expected, both as sorted lists
    actual, expected = evaluate_table(MonthlyAmounts, [*transactions, *monthly_amounts])

    assert actual == expected

5. Evaluate against a backend

from datetime import date

from ibis_typing import IbisConnection, evaluator
from ibis_typing.table_store import ParquetTableStore

conn = IbisConnection()  # defaults to in-memory DuckDB
transactions = Transaction.of_rows(  # give test data via IbisSchema rows.
    [Transaction(date=date(2024, 1, 15), amount=100.0, category="A")]
)
monthly_amounts = evaluator.from_expression(MonthlyAmounts, transactions)
results: list[MonthlyAmounts] = list(conn.fetch_table(monthly_amounts))

# Write and read parquet files locally, stored by schema name.
from pathlib import Path

store = ParquetTableStore(Path("/tmp/table_store"))
store.write_table(transactions)
table = store(Transaction)
rows: list[Transaction] = list(conn.fetch_table(table))

Core concepts

graph TD
    IbisSchema -->|describes| IbisTable
    IbisTable -->|In| Expression
    Expression -->|Out| IbisTable
    TableProvider -->|provides tables to| Expression
    IbisConnection -->|fetches typed rows from| IbisTable
    ChecksumBuckets -->|incremental inputs to| IncrementalExpression
    IncrementalExpression -->|is a| Expression
    BucketedInputsExpression -->|is a| IncrementalExpression
    RevertibleTableExpression -->|can revert| Expression

Loading

Class	Purpose
IbisSchema	Base class for typed table schemas (attrs frozen dataclass)
IbisTable[S]	Generic typed wrapper around ibis.Table
Expression	Abstract base for typed ibis transforms
TableMethod	Extension method on ibis.Table returning another Table
ValueMethod	Extension method on ibis.Value returning another Value
Deferred	table @ it.deferred.distinct() value @ it.defer().notnull()
IbisConnection	Typed backend wrapper: fetch_table(), evaluate(), read/write_parquet()
BucketedInputsExpression	Expression that only re-runs for changed input buckets
ChecksumBuckets	Checksum-based incremental input tracking
RevertibleTableExpression	Transform that can undo itself back to the original schema

Type aliases

Declare schema fields using column-type aliases from ibis_typing.it:

from ibis_typing import it

it.Int8, it.Int16, it.Int32, it.Int64
it.Float32, it.Float64
it.Boolean
it.String, it.Binary
it.Decimal
it.Date, it.Time, it.Timestamp
it.UUID, it.JSON
it.Array[it.Int64]
it.Map[it.String, it.Float64]
it.Struct[MyTypedDict]

Table operations

Use the infix @ operator for composable, typed table transforms via TableMethod. Standard Ibis Table methods are available via it.deferred.distinct(). Ibis Value methods are available via e.g. it.defer(type_=ir.Value).notnull().

from ibis_typing import IbisSchema, IbisTable, this, it


@frozen
class InputSchema(IbisSchema):
    a: it.Float64 = None
    b: it.Float64 = None
    category: it.String = None
    amount: it.Float64 = None
    key: it.String = None


inputs: IbisTable[InputSchema] = ...
other_table: IbisTable = ...
cols = InputSchema.cols

table = (
    inputs.table
    @ it.Select(cols.a, cols.b, expr={"c": this[cols.a] + this[cols.b]})
    @ it.Aggregate(by=[cols.category], sum=[cols.amount])
    @ it.InnerJoin(other_table.table, keys=[cols.key])
    @ it.deferred.filter(this[cols.amount] != 0)
)

Pytest fixtures

The following fixtures are auto-registered via the pytest plugin entry point (no conftest.py needed):

Fixture	Purpose
evaluate_table	Runs an Expression, returns (actual, expected) row lists
fetch_table	Fetches rows from an IbisTable
ibis_connection	Provides a IbisConnection for relevant DB backends

Extras

• ibis_typing.type_patch — patches installed ibis with typed @overload stubs for ibis.ifelse, ibis.cases, ibis.coalesce, etc.
• ibis_typing.schema_writer — code-gen: write IbisSchema .py files from Expression output schemas
• ibis_typing.plot — plots the dependency graph of an Expression using matplotlib/graphviz
• ibis_typing.custom — custom ibis operations: DateAddMonth, DateAddDay, ColumnChecksum, JsonParse, JsonFormat, UUIDFromInt, LuhnCheck

Contributing

git clone https://github.com/FortnoxAB/ibis-typing
cd ibis-typing
make

Pull requests welcome. Please run make before submitting.

License

MIT