Release: 2.0.35 | Release Date: September 16, 2024

# SQLAlchemy 2.0 Documentation

# Hybrid Attributes

Define attributes on ORM-mapped classes that have “hybrid” behavior.

“hybrid” means the attribute has distinct behaviors defined at the class level and at the instance level.

The `hybrid` extension provides a special form of method decorator and has minimal dependencies on the rest of SQLAlchemy. Its basic theory of operation can work with any descriptor-based expression system.

Consider a mapping `Interval`, representing integer `start` and `end` values. We can define higher level functions on mapped classes that produce SQL expressions at the class level, and Python expression evaluation at the instance level. Below, each function decorated with `hybrid_method` or `hybrid_property` may receive `self` as an instance of the class, or may receive the class directly, depending on context:

    from __future__ import annotations

    from sqlalchemy.ext.hybrid import hybrid_method
    from sqlalchemy.ext.hybrid import hybrid_property
    from sqlalchemy.orm import DeclarativeBase
    from sqlalchemy.orm import Mapped
    from sqlalchemy.orm import mapped_column

    class Base(DeclarativeBase):
        pass

    class Interval(Base):
        __tablename__ = 'interval'

        id: Mapped[int] = mapped_column(primary_key=True)
        start: Mapped[int]
        end: Mapped[int]

        def __init__(self, start: int, end: int):
            self.start = start
            self.end = end

        @hybrid_property
        def length(self) -> int:
            return self.end - self.start

        @hybrid_method
        def contains(self, point: int) -> bool:
            return (self.start <= point) & (point <= self.end)

        @hybrid_method
        def intersects(self, other: Interval) -> bool:
            return self.contains(other.start) | self.contains(other.end)

Above, the `length` property returns the difference between the `end` and `start` attributes. With an instance of `Interval`, this subtraction occurs in Python, using normal Python descriptor mechanics:

    >>> i1 = Interval(5, 10)
    >>> i1.length
    5

When dealing with the `Interval` class itself, the `hybrid_property` descriptor evaluates the function body given the `Interval` class as the argument, which when evaluated with SQLAlchemy expression mechanics returns a new SQL expression:

    >>> from sqlalchemy import select
    >>> print(select(Interval.length))
    SELECT interval."end" - interval.start AS length
    FROM interval
    >>> print(select(Interval).filter(Interval.length > 10))
    SELECT interval.id, interval.start, interval."end"
    FROM interval
    WHERE interval."end" - interval.start > :param_1

Filtering methods such as `Select.filter_by()` are supported with hybrid attributes as well:

    >>> print(select(Interval).filter_by(length=5))
    SELECT interval.id, interval.start, interval."end"
    FROM interval
    WHERE interval."end" - interval.start = :param_1

The `Interval` class example also illustrates two methods, `contains()` and `intersects()`, decorated with `hybrid_method`. This decorator applies the same idea to methods that `hybrid_property` applies to attributes. The methods return boolean values, and take advantage of the Python `|` and `&` bitwise operators to produce equivalent instance-level and SQL expression-level boolean behavior:

    >>> i1.contains(6)
    True
    >>> i1.contains(15)
    False
    >>> i1.intersects(Interval(7, 18))
    True
    >>> i1.intersects(Interval(25, 29))
    False

    >>> print(select(Interval).filter(Interval.contains(15)))
    SELECT interval.id, interval.start, interval."end"
    FROM interval
    WHERE interval.start <= :start_1 AND interval."end" > :end_1
    >>> ia = aliased(Interval)
    >>> print(select(Interval, ia).filter(Interval.intersects(ia)))
    SELECT interval.id, interval.start,
    interval."end", interval_1.id AS interval_1_id,
    interval_1.start AS interval_1_start, interval_1."end" AS interval_1_end
    FROM interval, interval AS interval_1
    WHERE interval.start <= interval_1.start
        AND interval."end" > interval_1.start
        OR interval.start <= interval_1."end"
        AND interval."end" > interval_1."end"

## Defining Expression Behavior Distinct from Attribute Behavior

In the previous section, our usage of the `&` and `|` bitwise operators within the `Interval.contains` and `Interval.intersects` methods was fortunate, considering our functions operated on two boolean values to return a new one. In many cases, the construction of an in-Python function and a SQLAlchemy SQL expression have enough differences that two separate Python expressions should be defined. The `hybrid` decorator defines a modifier `hybrid_property.expression()` for this purpose. As an example we’ll define the radius of the interval, which requires the usage of the absolute value function:

    from sqlalchemy import ColumnElement
    from sqlalchemy import Float
    from sqlalchemy import func
    from sqlalchemy import type_coerce

    class Interval(Base):
        # ...

        @hybrid_property
        def radius(self) -> float:
            return abs(self.length) / 2

        @radius.inplace.expression
        @classmethod
        def _radius_expression(cls) -> ColumnElement[float]:
            return type_coerce(func.abs(cls.length) / 2, Float)

In the above example, the `hybrid_property` first assigned to the name `Interval.radius` is amended by a subsequent method called `Interval._radius_expression`, using the decorator `@radius.inplace.expression`, which chains together two modifiers `hybrid_property.inplace` and `hybrid_property.expression`. The use of `hybrid_property.inplace` indicates that the `hybrid_property.expression()` modifier should mutate the existing hybrid object at `Interval.radius` in place, without creating a new object. Notes on this modifier and its rationale are discussed in the next section Using inplace to create pep-484 compliant hybrid properties. The use of `@classmethod` is optional, and is strictly to give typing tools a hint that `cls` in this case is expected to be the `Interval` class, and not an instance of `Interval`.

Note

`hybrid_property.inplace` as well as the use of `@classmethod` for proper typing support are available as of SQLAlchemy 2.0.4, and will not work in earlier versions.

With `Interval.radius` now including an expression element, the SQL function `ABS()` is returned when accessing `Interval.radius` at the class level:

    >>> from sqlalchemy import select
    >>> print(select(Interval).filter(Interval.radius > 5))
    SELECT interval.id, interval.start, interval."end"
    FROM interval
    WHERE abs(interval."end" - interval.start) / :abs_1 > :param_1

## Using `inplace` to create pep-484 compliant hybrid properties

In the previous section, a `hybrid_property` decorator is illustrated which includes two separate method-level functions being decorated, both to produce a single object attribute referenced as `Interval.radius`. There are actually several different modifiers we can use for `hybrid_property` including `hybrid_property.expression()`, `hybrid_property.setter()` and `hybrid_property.update_expression()`.

SQLAlchemy’s `hybrid_property` decorator intends that adding on these methods may be done in the identical manner as Python’s built-in `@property` decorator, where idiomatic use is to continue to redefine the attribute repeatedly, using the same attribute name each time, as in the example below that illustrates the use of `hybrid_property.setter()` and `hybrid_property.expression()` for the `Interval.radius` descriptor:

    # correct use, however is not accepted by pep-484 tooling

    class Interval(Base):
        # ...

        @hybrid_property
        def radius(self):
            return abs(self.length) / 2

        @radius.setter
        def radius(self, value):
            self.length = value * 2

        @radius.expression
        def radius(cls):
            return type_coerce(func.abs(cls.length) / 2, Float)

Above, there are three `Interval.radius` methods, but as each are decorated, first by the `hybrid_property` decorator and then by the `@radius` name itself, the end effect is that `Interval.radius` is a single attribute with three different functions contained within it. This style of use is taken from Python’s documented use of @property. It is important to note that the way both `@property` as well as `hybrid_property` work, a copy of the descriptor is made each time. That is, each call to `@radius.expression`, `@radius.setter` etc. make a new object entirely. This allows the attribute to be re-defined in subclasses without issue (see Reusing Hybrid Properties across Subclasses later in this section for how this is used).

However, the above approach is not compatible with typing tools such as mypy and pyright. Python’s own `@property` decorator does not have this limitation only because these tools hardcode the behavior of @property, meaning this syntax is not available to SQLAlchemy under PEP 484 compliance.

In order to produce a reasonable syntax while remaining typing compliant, the `hybrid_property.inplace` decorator allows the same decorator to be re-used with different method names, while still producing a single decorator under one name:

    # correct use which is also accepted by pep-484 tooling

    class Interval(Base):
        # ...

        @hybrid_property
        def radius(self) -> float:
            return abs(self.length) / 2

        @radius.inplace.setter
        def _radius_setter(self, value: float) -> None:
            # for example only
            self.length = value * 2

        @radius.inplace.expression
        @classmethod
        def _radius_expression(cls) -> ColumnElement[float]:
            return type_coerce(func.abs(cls.length) / 2, Float)

Using `hybrid_property.inplace` further qualifies the use of the decorator that a new copy should not be made, thereby maintaining the `Interval.radius` name while allowing additional methods `Interval._radius_setter` and `Interval._radius_expression` to be differently named.

New in version 2.0.4: Added `hybrid_property.inplace` to allow less verbose construction of composite `hybrid_property` objects while not having to use repeated method names. Additionally allowed the use of `@classmethod` within `hybrid_property.expression`, `hybrid_property.update_expression`, and `hybrid_property.comparator` to allow typing tools to identify `cls` as a class and not an instance in the method signature.

## Defining Setters

The `hybrid_property.setter()` modifier allows the construction of a custom setter method, that can modify values on the object:

    class Interval(Base):
        # ...

        @hybrid_property
        def length(self) -> int:
            return self.end - self.start

        @length.inplace.setter
        def _length_setter(self, value: int) -> None:
            self.end = self.start + value

The `length(self, value)` method is now called upon set:

    >>> i1 = Interval(5, 10)
    >>> i1.length
    5
    >>> i1.length = 12
    >>> i1.end
    17

## Allowing Bulk ORM Update

A hybrid can define a custom “UPDATE” handler for when using ORM-enabled updates, allowing the hybrid to be used in the SET clause of the update.

Normally, when using a hybrid with `update()`, the SQL expression is used as the column that’s the target of the SET. If our `Interval` class had a hybrid `start_point` that linked to `Interval.start`, this could be substituted directly:

    from sqlalchemy import update
    stmt = update(Interval).values({Interval.start_point: 10})

However, when using a composite hybrid like `Interval.length`, this hybrid represents more than one column. We can set up a handler that will accommodate a value passed in the VALUES expression which can affect this, using the `hybrid_property.update_expression()` decorator. A handler that works similarly to our setter would be:

    from typing import List, Tuple, Any

    class Interval(Base):
        # ...

        @hybrid_property
        def length(self) -> int:
            return self.end - self.start

        @length.inplace.setter
        def _length_setter(self, value: int) -> None:
            self.end = self.start + value

        @length.inplace.update_expression
        def _length_update_expression(cls, value: Any) -> List[Tuple[Any, Any]]:
            return [
                (cls.end, cls.start + value)
            ]

Above, if we use `Interval.length` in an UPDATE expression, we get a hybrid SET expression:

    >>> from sqlalchemy import update
    >>> print(update(Interval).values({Interval.length: 25}))
    UPDATE interval SET "end"=(interval.start + :start_1)

This SET expression is accommodated by the ORM automatically.

See also

ORM-Enabled INSERT, UPDATE, and DELETE statements - includes background on ORM-enabled UPDATE statements

## Working with Relationships

There’s no essential difference when creating hybrids that work with related objects as opposed to column-based data. The need for distinct expressions tends to be greater. The two variants we’ll illustrate are the “join-dependent” hybrid, and the “correlated subquery” hybrid.

### Join-Dependent Relationship Hybrid

Consider the following declarative mapping which relates a `User` to a `SavingsAccount`:

    from __future__ import annotations

    from decimal import Decimal
    from typing import cast
    from typing import List
    from typing import Optional

    from sqlalchemy import ForeignKey
    from sqlalchemy import Numeric
    from sqlalchemy import String
    from sqlalchemy import SQLColumnExpression
    from sqlalchemy.ext.hybrid import hybrid_property
    from sqlalchemy.orm import DeclarativeBase
    from sqlalchemy.orm import Mapped
    from sqlalchemy.orm import mapped_column
    from sqlalchemy.orm import relationship

    class Base(DeclarativeBase):
        pass

    class SavingsAccount(Base):
        __tablename__ = 'account'
        id: Mapped[int] = mapped_column(primary_key=True)
        user_id: Mapped[int] = mapped_column(ForeignKey('user.id'))
        balance: Mapped[Decimal] = mapped_column(Numeric(15, 5))

        owner: Mapped[User] = relationship(back_populates="accounts")

    class User(Base):
        __tablename__ = 'user'
        id: Mapped[int] = mapped_column(primary_key=True)
        name: Mapped[str] = mapped_column(String(100))

        accounts: Mapped[List[SavingsAccount]] = relationship(
            back_populates="owner", lazy="selectin"
        )

        @hybrid_property
        def balance(self) -> Optional[Decimal]:
            if self.accounts:
                return self.accounts[0].balance
            else:
                return None

        @balance.inplace.setter
        def _balance_setter(self, value: Optional[Decimal]) -> None:
            assert value is not None

            if not self.accounts:
                account = SavingsAccount(owner=self)
            else:
                account = self.accounts[0]
            account.balance = value

        @balance.inplace.expression
        @classmethod
        def _balance_expression(cls) -> SQLColumnExpression[Optional[Decimal]]:
            return cast("SQLColumnExpression[Optional[Decimal]]", SavingsAccount.balance)

The above hybrid property `balance` works with the first `SavingsAccount` entry in the list of accounts for this user. The in-Python getter/setter methods can treat `accounts` as a Python list available on `self`.

Tip

The `User.balance` getter in the above example accesses the `self.acccounts` collection, which will normally be loaded via the `selectinload()` loader strategy configured on the `User.balance` `relationship()`. The default loader strategy when not otherwise stated on `relationship()` is `lazyload()`, which emits SQL on demand. When using asyncio, on-demand loaders such as `lazyload()` are not supported, so care should be taken to ensure the `self.accounts` collection is accessible to this hybrid accessor when using asyncio.

At the expression level, it’s expected that the `User` class will be used in an appropriate context such that an appropriate join to `SavingsAccount` will be present:

    >>> from sqlalchemy import select
    >>> print(select(User, User.balance).
    ...       join(User.accounts).filter(User.balance > 5000))
    SELECT "user".id AS user_id, "user".name AS user_name,
    account.balance AS account_balance
    FROM "user" JOIN account ON "user".id = account.user_id
    WHERE account.balance > :balance_1

Note however, that while the instance level accessors need to worry about whether `self.accounts` is even present, this issue expresses itself differently at the SQL expression level, where we basically would use an outer join:

    >>> from sqlalchemy import select
    >>> from sqlalchemy import or_
    >>> print (select(User, User.balance).outerjoin(User.accounts).
    ...         filter(or_(User.balance < 5000, User.balance == None)))
    SELECT "user".id AS user_id, "user".name AS user_name,
    account.balance AS account_balance
    FROM "user" LEFT OUTER JOIN account ON "user".id = account.user_id
    WHERE account.balance <  :balance_1 OR account.balance IS NULL

### Correlated Subquery Relationship Hybrid

We can, of course, forego being dependent on the enclosing query’s usage of joins in favor of the correlated subquery, which can portably be packed into a single column expression. A correlated subquery is more portable, but often performs more poorly at the SQL level. Using the same technique illustrated at Using column_property, we can adjust our `SavingsAccount` example to aggregate the balances for all accounts, and use a correlated subquery for the column expression:

    from __future__ import annotations

    from decimal import Decimal
    from typing import List

    from sqlalchemy import ForeignKey
    from sqlalchemy import func
    from sqlalchemy import Numeric
    from sqlalchemy import select
    from sqlalchemy import SQLColumnExpression
    from sqlalchemy import String
    from sqlalchemy.ext.hybrid import hybrid_property
    from sqlalchemy.orm import DeclarativeBase
    from sqlalchemy.orm import Mapped
    from sqlalchemy.orm import mapped_column
    from sqlalchemy.orm import relationship

    class Base(DeclarativeBase):
        pass

    class SavingsAccount(Base):
        __tablename__ = 'account'
        id: Mapped[int] = mapped_column(primary_key=True)
        user_id: Mapped[int] = mapped_column(ForeignKey('user.id'))
        balance: Mapped[Decimal] = mapped_column(Numeric(15, 5))

        owner: Mapped[User] = relationship(back_populates="accounts")

    class User(Base):
        __tablename__ = 'user'
        id: Mapped[int] = mapped_column(primary_key=True)
        name: Mapped[str] = mapped_column(String(100))

        accounts: Mapped[List[SavingsAccount]] = relationship(
            back_populates="owner", lazy="selectin"
        )

        @hybrid_property
        def balance(self) -> Decimal:
            return sum((acc.balance for acc in self.accounts), start=Decimal("0"))

        @balance.inplace.expression
        @classmethod
        def _balance_expression(cls) -> SQLColumnExpression[Decimal]:
            return (
                select(func.sum(SavingsAccount.balance))
                .where(SavingsAccount.user_id == cls.id)
                .label("total_balance")
            )

The above recipe will give us the `balance` column which renders a correlated SELECT:

    >>> from sqlalchemy import select
    >>> print(select(User).filter(User.balance > 400))
    SELECT "user".id, "user".name
    FROM "user"
    WHERE (
        SELECT sum(account.balance) AS sum_1 FROM account
        WHERE account.user_id = "user".id
    ) > :param_1

## Building Custom Comparators

The hybrid property also includes a helper that allows construction of custom comparators. A comparator object allows one to customize the behavior of each SQLAlchemy expression operator individually. They are useful when creating custom types that have some highly idiosyncratic behavior on the SQL side.

Note

The `hybrid_property.comparator()` decorator introduced in this section replaces the use of the `hybrid_property.expression()` decorator. They cannot be used together.

The example class below allows case-insensitive comparisons on the attribute named `word_insensitive`:

    from __future__ import annotations

    from typing import Any

    from sqlalchemy import ColumnElement
    from sqlalchemy import func
    from sqlalchemy.ext.hybrid import Comparator
    from sqlalchemy.ext.hybrid import hybrid_property
    from sqlalchemy.orm import DeclarativeBase
    from sqlalchemy.orm import Mapped
    from sqlalchemy.orm import mapped_column

    class Base(DeclarativeBase):
        pass

    class CaseInsensitiveComparator(Comparator[str]):
        def __eq__(self, other: Any) -> ColumnElement[bool]:  # type: ignore[override]  # noqa: E501
            return func.lower(self.__clause_element__()) == func.lower(other)

    class SearchWord(Base):
        __tablename__ = 'searchword'

        id: Mapped[int] = mapped_column(primary_key=True)
        word: Mapped[str]

        @hybrid_property
        def word_insensitive(self) -> str:
            return self.word.lower()

        @word_insensitive.inplace.comparator
        @classmethod
        def _word_insensitive_comparator(cls) -> CaseInsensitiveComparator:
            return CaseInsensitiveComparator(cls.word)

Above, SQL expressions against `word_insensitive` will apply the `LOWER()` SQL function to both sides:

    >>> from sqlalchemy import select
    >>> print(select(SearchWord).filter_by(word_insensitive="Trucks"))
    SELECT searchword.id, searchword.word
    FROM searchword
    WHERE lower(searchword.word) = lower(:lower_1)

The `CaseInsensitiveComparator` above implements part of the `ColumnOperators` interface. A “coercion” operation like lowercasing can be applied to all comparison operations (i.e. `eq`, `lt`, `gt`, etc.) using `Operators.operate()`:

    class CaseInsensitiveComparator(Comparator):
        def operate(self, op, other, **kwargs):
            return op(
                func.lower(self.__clause_element__()),
                func.lower(other),
                **kwargs,
            )

## Reusing Hybrid Properties across Subclasses

A hybrid can be referred to from a superclass, to allow modifying methods like `hybrid_property.getter()`, `hybrid_property.setter()` to be used to redefine those methods on a subclass. This is similar to how the standard Python `@property` object works:

    class FirstNameOnly(Base):
        # ...

        first_name: Mapped[str]

        @hybrid_property
        def name(self) -> str:
            return self.first_name

        @name.inplace.setter
        def _name_setter(self, value: str) -> None:
            self.first_name = value

    class FirstNameLastName(FirstNameOnly):
        # ...

        last_name: Mapped[str]

        # 'inplace' is not used here; calling getter creates a copy
        # of FirstNameOnly.name that is local to FirstNameLastName
        @FirstNameOnly.name.getter
        def name(self) -> str:
            return self.first_name + ' ' + self.last_name

        @name.inplace.setter
        def _name_setter(self, value: str) -> None:
            self.first_name, self.last_name = value.split(' ', 1)

Above, the `FirstNameLastName` class refers to the hybrid from `FirstNameOnly.name` to repurpose its getter and setter for the subclass.

When overriding `hybrid_property.expression()` and `hybrid_property.comparator()` alone as the first reference to the superclass, these names conflict with the same-named accessors on the class- level `QueryableAttribute` object returned at the class level. To override these methods when referring directly to the parent class descriptor, add the special qualifier `hybrid_property.overrides`, which will de- reference the instrumented attribute back to the hybrid object:

    class FirstNameLastName(FirstNameOnly):
        # ...

        last_name: Mapped[str]

        @FirstNameOnly.name.overrides.expression
        @classmethod
        def name(cls):
            return func.concat(cls.first_name, ' ', cls.last_name)

## Hybrid Value Objects

Note in our previous example, if we were to compare the `word_insensitive` attribute of a `SearchWord` instance to a plain Python string, the plain Python string would not be coerced to lower case - the `CaseInsensitiveComparator` we built, being returned by `@word_insensitive.comparator`, only applies to the SQL side.

A more comprehensive form of the custom comparator is to construct a Hybrid Value Object. This technique applies the target value or expression to a value object which is then returned by the accessor in all cases. The value object allows control of all operations upon the value as well as how compared values are treated, both on the SQL expression side as well as the Python value side. Replacing the previous `CaseInsensitiveComparator` class with a new `CaseInsensitiveWord` class:

    class CaseInsensitiveWord(Comparator):
        "Hybrid value representing a lower case representation of a word."

        def __init__(self, word):
            if isinstance(word, basestring):
                self.word = word.lower()
            elif isinstance(word, CaseInsensitiveWord):
                self.word = word.word
            else:
                self.word = func.lower(word)

        def operate(self, op, other, **kwargs):
            if not isinstance(other, CaseInsensitiveWord):
                other = CaseInsensitiveWord(other)
            return op(self.word, other.word, **kwargs)

        def __clause_element__(self):
            return self.word

        def __str__(self):
            return self.word

        key = 'word'
        "Label to apply to Query tuple results"

Above, the `CaseInsensitiveWord` object represents `self.word`, which may be a SQL function, or may be a Python native. By overriding `operate()` and `__clause_element__()` to work in terms of `self.word`, all comparison operations will work against the “converted” form of `word`, whether it be SQL side or Python side. Our `SearchWord` class can now deliver the `CaseInsensitiveWord` object unconditionally from a single hybrid call:

    class SearchWord(Base):
        __tablename__ = 'searchword'
        id: Mapped[int] = mapped_column(primary_key=True)
        word: Mapped[str]

        @hybrid_property
        def word_insensitive(self) -> CaseInsensitiveWord:
            return CaseInsensitiveWord(self.word)

The `word_insensitive` attribute now has case-insensitive comparison behavior universally, including SQL expression vs. Python expression (note the Python value is converted to lower case on the Python side here):

    >>> print(select(SearchWord).filter_by(word_insensitive="Trucks"))
    SELECT searchword.id AS searchword_id, searchword.word AS searchword_word
    FROM searchword
    WHERE lower(searchword.word) = :lower_1

SQL expression versus SQL expression:

    >>> from sqlalchemy.orm import aliased
    >>> sw1 = aliased(SearchWord)
    >>> sw2 = aliased(SearchWord)
    >>> print(
    ...     select(sw1.word_insensitive, sw2.word_insensitive).filter(
    ...         sw1.word_insensitive > sw2.word_insensitive
    ...     )
    ... )
    SELECT lower(searchword_1.word) AS lower_1,
    lower(searchword_2.word) AS lower_2
    FROM searchword AS searchword_1, searchword AS searchword_2
    WHERE lower(searchword_1.word) > lower(searchword_2.word)

Python only expression:

    >>> ws1 = SearchWord(word="SomeWord")
    >>> ws1.word_insensitive == "sOmEwOrD"
    True
    >>> ws1.word_insensitive == "XOmEwOrX"
    False
    >>> print(ws1.word_insensitive)
    someword

The Hybrid Value pattern is very useful for any kind of value that may have multiple representations, such as timestamps, time deltas, units of measurement, currencies and encrypted passwords.

See also

Hybrids and Value Agnostic Types - on the techspot.zzzeek.org blog

Value Agnostic Types, Part II - on the techspot.zzzeek.org blog

## API Reference

Object Name | Description
--- | ---
Comparator | A helper class that allows easy construction of custom `PropComparator` classes for usage with hybrids.
hybrid_method | A decorator which allows definition of a Python object method with both instance-level and class-level behavior.
hybrid_property | A decorator which allows definition of a Python descriptor with both instance-level and class-level behavior.
HybridExtensionType |

class sqlalchemy.ext.hybrid.hybrid_method

  A decorator which allows definition of a Python object method with both instance-level and class-level behavior.

  Members

  __init__(), expression(), extension_type, inplace, is_attribute

  Class signature

  class `sqlalchemy.ext.hybrid.hybrid_method` (`sqlalchemy.orm.base.InspectionAttrInfo`, `typing.Generic`)

  method `sqlalchemy.ext.hybrid.hybrid_method.`__init__(func: Callable[[Concatenate[Any, _P]], _R], expr: Callable[[Concatenate[Any, _P]], SQLCoreOperations[_R]] | None = None)

    Create a new `hybrid_method`.

    Usage is typically via decorator:

        from sqlalchemy.ext.hybrid import hybrid_method

        class SomeClass:
            @hybrid_method
            def value(self, x, y):
                return self._value + x + y

            @value.expression
            @classmethod
            def value(cls, x, y):
                return func.some_function(cls._value, x, y)

  method `sqlalchemy.ext.hybrid.hybrid_method.`expression(expr: Callable[[Concatenate[Any, _P]], SQLCoreOperations[_R]]) → hybrid_method[_P, _R]

    Provide a modifying decorator that defines a SQL-expression producing method.

  attribute `sqlalchemy.ext.hybrid.hybrid_method.`extension_type: InspectionAttrExtensionType = 'HYBRID_METHOD'

    The extension type, if any. Defaults to `NotExtension.NOT_EXTENSION`

    See also

    `HybridExtensionType`

    `AssociationProxyExtensionType`

  attribute `sqlalchemy.ext.hybrid.hybrid_method.`inplace

    Return the inplace mutator for this `hybrid_method`.

    The `hybrid_method` class already performs “in place” mutation when the `hybrid_method.expression()` decorator is called, so this attribute returns Self.

    New in version 2.0.4.

    See also

    Using inplace to create pep-484 compliant hybrid properties

  attribute `sqlalchemy.ext.hybrid.hybrid_method.`is_attribute = True

    True if this object is a Python descriptor.

    This can refer to one of many types. Usually a `QueryableAttribute` which handles attributes events on behalf of a `MapperProperty`. But can also be an extension type such as `AssociationProxy` or `hybrid_property`. The `InspectionAttr.extension_type` will refer to a constant identifying the specific subtype.

    See also

    `Mapper.all_orm_descriptors`

class sqlalchemy.ext.hybrid.hybrid_property

  A decorator which allows definition of a Python descriptor with both instance-level and class-level behavior.

  Members

  __init__(), comparator(), deleter(), expression(), extension_type, getter(), inplace, is_attribute, overrides, setter(), update_expression()

  Class signature

  class `sqlalchemy.ext.hybrid.hybrid_property` (`sqlalchemy.orm.base.InspectionAttrInfo`, `sqlalchemy.orm.base.ORMDescriptor`)

  method `sqlalchemy.ext.hybrid.hybrid_property.`__init__(fget: _HybridGetterType[_T], fset: _HybridSetterType[_T] | None = None, fdel: _HybridDeleterType[_T] | None = None, expr: _HybridExprCallableType[_T] | None = None, custom_comparator: Comparator[_T] | None = None, update_expr: _HybridUpdaterType[_T] | None = None)

    Create a new `hybrid_property`.

    Usage is typically via decorator:

        from sqlalchemy.ext.hybrid import hybrid_property

        class SomeClass:
            @hybrid_property
            def value(self):
                return self._value

            @value.setter
            def value(self, value):
                self._value = value

  method `sqlalchemy.ext.hybrid.hybrid_property.`comparator(comparator: _HybridComparatorCallableType[_T]) → hybrid_property[_T]

    Provide a modifying decorator that defines a custom comparator producing method.

    The return value of the decorated method should be an instance of `Comparator`.

    Note

    The `hybrid_property.comparator()` decorator replaces the use of the `hybrid_property.expression()` decorator. They cannot be used together.

    When a hybrid is invoked at the class level, the `Comparator` object given here is wrapped inside of a specialized `QueryableAttribute`, which is the same kind of object used by the ORM to represent other mapped attributes. The reason for this is so that other class-level attributes such as docstrings and a reference to the hybrid itself may be maintained within the structure that’s returned, without any modifications to the original comparator object passed in.

    Note

    When referring to a hybrid property from an owning class (e.g. `SomeClass.some_hybrid`), an instance of `QueryableAttribute` is returned, representing the expression or comparator object as this hybrid object. However, that object itself has accessors called `expression` and `comparator`; so when attempting to override these decorators on a subclass, it may be necessary to qualify it using the `hybrid_property.overrides` modifier first. See that modifier for details.

  method `sqlalchemy.ext.hybrid.hybrid_property.`deleter(fdel: _HybridDeleterType[_T]) → hybrid_property[_T]

    Provide a modifying decorator that defines a deletion method.

  method `sqlalchemy.ext.hybrid.hybrid_property.`expression(expr: _HybridExprCallableType[_T]) → hybrid_property[_T]

    Provide a modifying decorator that defines a SQL-expression producing method.

    When a hybrid is invoked at the class level, the SQL expression given here is wrapped inside of a specialized `QueryableAttribute`, which is the same kind of object used by the ORM to represent other mapped attributes. The reason for this is so that other class-level attributes such as docstrings and a reference to the hybrid itself may be maintained within the structure that’s returned, without any modifications to the original SQL expression passed in.

    Note

    When referring to a hybrid property from an owning class (e.g. `SomeClass.some_hybrid`), an instance of `QueryableAttribute` is returned, representing the expression or comparator object as well as this hybrid object. However, that object itself has accessors called `expression` and `comparator`; so when attempting to override these decorators on a subclass, it may be necessary to qualify it using the `hybrid_property.overrides` modifier first. See that modifier for details.

    See also

    Defining Expression Behavior Distinct from Attribute Behavior

  attribute `sqlalchemy.ext.hybrid.hybrid_property.`extension_type: InspectionAttrExtensionType = 'HYBRID_PROPERTY'

    The extension type, if any. Defaults to `NotExtension.NOT_EXTENSION`

    See also

    `HybridExtensionType`

    `AssociationProxyExtensionType`

  method `sqlalchemy.ext.hybrid.hybrid_property.`getter(fget: _HybridGetterType[_T]) → hybrid_property[_T]

    Provide a modifying decorator that defines a getter method.

    New in version 1.2.

  attribute `sqlalchemy.ext.hybrid.hybrid_property.`inplace

    Return the inplace mutator for this `hybrid_property`.

    This is to allow in-place mutation of the hybrid, allowing the first hybrid method of a certain name to be re-used in order to add more methods without having to name those methods the same, e.g.:

        class Interval(Base):
            # ...

            @hybrid_property
            def radius(self) -> float:
                return abs(self.length) / 2

            @radius.inplace.setter
            def _radius_setter(self, value: float) -> None:
                self.length = value * 2

            @radius.inplace.expression
            def _radius_expression(cls) -> ColumnElement[float]:
                return type_coerce(func.abs(cls.length) / 2, Float)

    New in version 2.0.4.

    See also

    Using inplace to create pep-484 compliant hybrid properties

  attribute `sqlalchemy.ext.hybrid.hybrid_property.`is_attribute = True

    True if this object is a Python descriptor.

    This can refer to one of many types. Usually a `QueryableAttribute` which handles attributes events on behalf of a `MapperProperty`. But can also be an extension type such as `AssociationProxy` or `hybrid_property`. The `InspectionAttr.extension_type` will refer to a constant identifying the specific subtype.

    See also

    `Mapper.all_orm_descriptors`

  attribute `sqlalchemy.ext.hybrid.hybrid_property.`overrides

    Prefix for a method that is overriding an existing attribute.

    The `hybrid_property.overrides` accessor just returns this hybrid object, which when called at the class level from a parent class, will de-reference the “instrumented attribute” normally returned at this level, and allow modifying decorators like `hybrid_property.expression()` and `hybrid_property.comparator()` to be used without conflicting with the same-named attributes normally present on the `QueryableAttribute`:

        class SuperClass:
            # ...

            @hybrid_property
            def foobar(self):
                return self._foobar

        class SubClass(SuperClass):
            # ...

            @SuperClass.foobar.overrides.expression
            def foobar(cls):
                return func.subfoobar(self._foobar)

    New in version 1.2.

    See also

    Reusing Hybrid Properties across Subclasses

  method `sqlalchemy.ext.hybrid.hybrid_property.`setter(fset: _HybridSetterType[_T]) → hybrid_property[_T]

    Provide a modifying decorator that defines a setter method.

  method `sqlalchemy.ext.hybrid.hybrid_property.`update_expression(meth: _HybridUpdaterType[_T]) → hybrid_property[_T]

    Provide a modifying decorator that defines an UPDATE tuple producing method.

    The method accepts a single value, which is the value to be rendered into the SET clause of an UPDATE statement. The method should then process this value into individual column expressions that fit into the ultimate SET clause, and return them as a sequence of 2-tuples. Each tuple contains a column expression as the key and a value to be rendered.

    E.g.:

        class Person(Base):
            # ...

            first_name = Column(String)
            last_name = Column(String)

            @hybrid_property
            def fullname(self):
                return first_name + " " + last_name

            @fullname.update_expression
            def fullname(cls, value):
                fname, lname = value.split(" ", 1)
                return [
                    (cls.first_name, fname),
                    (cls.last_name, lname)
                ]

    New in version 1.2.

class sqlalchemy.ext.hybrid.Comparator

  A helper class that allows easy construction of custom `PropComparator` classes for usage with hybrids.

  Class signature

  class `sqlalchemy.ext.hybrid.Comparator` (`sqlalchemy.orm.PropComparator`)

class sqlalchemy.ext.hybrid.HybridExtensionType

  Members

  HYBRID_METHOD, HYBRID_PROPERTY

  Class signature

  class `sqlalchemy.ext.hybrid.HybridExtensionType` (`sqlalchemy.orm.base.InspectionAttrExtensionType`)

  attribute `sqlalchemy.ext.hybrid.HybridExtensionType.`HYBRID_METHOD = 'HYBRID_METHOD'

    Symbol indicating an `InspectionAttr` that’s of type `hybrid_method`.

    Is assigned to the `InspectionAttr.extension_type` attribute.

    See also

    `Mapper.all_orm_attributes`

  attribute `sqlalchemy.ext.hybrid.HybridExtensionType.`HYBRID_PROPERTY = 'HYBRID_PROPERTY'
    Symbol indicating an `InspectionAttr` that’s

      of type `hybrid_method`.

    Is assigned to the `InspectionAttr.extension_type` attribute.

    See also

    `Mapper.all_orm_attributes`