set()#

relationalai.Instance
Instance.set(*args, **kwargs) -> Instance

Set properties and assign types to an Instance object and return the Instance. Must be used in a rule or query context.

Parameters#

NameTypeDescription
*argsTypeOptional types to apply to the object.
*kwargsAnyProperties to set on the Instance, using <property_name>=<value>. Accepts Producer objects, numbers, strings, dates, and datetime objects.

Returns#

Returns the Instance object on which the property or type is set.

Example#

Use .set() to set properties and assign types to an object in your model:

import relationalai as rai

# Create a model named "people" with a Person type.
model = rai.Model("people")
Person = model.Type("Person")
Musician = model.Type("Musician")

with model.rule():
    # Add Person named "Kermit" to the model.
    kermit = Person.add(name="Kermit")
    # Set Kermit as a Musician and set his favorite_color property to "green."
    kermit.set(Musician, favorite_color="green")

Both Type.add() and Instance.set() set properties on objects. Person.add() initially adds an object with the name property set to "Kermit" and assigns it to the variable kermit. Subsequently, kermit.set(Musician, favorite_color="green") assigns the Musician type to the kermit object and sets his favorite_color to “green”. Unlike Instance.set(), properties set by Type.add() function like primary keys in a SQL database, uniquely identifying each object.

You can assign multiple types and set several properties simultaneously by passing multiple Type objects as positional arguments and multiple property values as keyword arguments to .set().

Properties created by both Type.add() and Instance.set() are single-valued. Setting a property a second time overwrites the previous value:

# Get Kermit's favorite color.
with model.query() as select:
    person = Person(name="Kermit")
    response = select(person.favorite_color)

# Currently, it is "green."
print(response.results)
# Output:
#   favorite_color
# 0          green

# Change Kermit's favorite color to "blue."
with model.rule():
    kermit = Person(name="Kermit")
    kermit.set(favorite_color="blue")

# Get Kermit's favorite color again.
with model.query() as select:
    person = Person(name="Kermit")
    response = select(person.favorite_color)

print(response.results)
# Output:
#   favorite_color
# 0           blue

Attempting to set a multi-valued property using .set() raises an Exception:

# Add a friends property to Kermit.
# friends is a multi-valued property because it is created with InstanceProperty.extend().
with model.rule():
    kermit = Person(name="Kermit")
    kermit.friends.extend(["Fozzie", "Miss Piggy", "Rowlf"])

# Attempt to set friends to "Gonzo" using .set().
with model.rule():
    kermit = Person(name="Kermit")
    kermit.set(friends="Gonzo")

# Output:
# Exception: Trying to use a property `friends` as both singular and multi-valued

See the InstanceProperty documentation for more information on multi-valued properties.

See Also#