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:

>>> fromsqlalchemyimportselect>>> 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:

>>> fromsqlalchemyimportselect>>> 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:

>>> fromsqlalchemyimportupdate>>> 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:

>>> fromsqlalchemyimportselect>>> 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:

>>> fromsqlalchemyimportselect>>> fromsqlalchemyimportor_>>> 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:

>>> fromsqlalchemyimportselect>>> 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:

>>> fromsqlalchemyimportselect>>> 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:

>>> fromsqlalchemy.ormimportaliased>>> 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.

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.

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.

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.

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

SQLAlchemy 2.0 Documentation

SQLAlchemy 2.0 Documentation

SQLAlchemy ORM

Hybrid Attributes¶

Defining Expression Behavior Distinct from Attribute Behavior¶

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

Defining Setters¶

Allowing Bulk ORM Update¶

Working with Relationships¶

Join-Dependent Relationship Hybrid¶

Correlated Subquery Relationship Hybrid¶

Building Custom Comparators¶

Reusing Hybrid Properties across Subclasses¶

Hybrid Value Objects¶

API Reference¶

SQLAlchemy 2.0 Documentation

SQLAlchemy 2.0 Documentation

SQLAlchemy ORM

Hybrid Attributes¶

Defining Expression Behavior Distinct from Attribute Behavior¶

Using inplace to create pep-484 compliant hybrid properties¶

Defining Setters¶

Allowing Bulk ORM Update¶

Working with Relationships¶

Join-Dependent Relationship Hybrid¶

Correlated Subquery Relationship Hybrid¶

Building Custom Comparators¶

Reusing Hybrid Properties across Subclasses¶

Hybrid Value Objects¶

API Reference¶

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