enter()#

relationalai.Producer
Producer.__enter__() -> None

Producer objects can be used as context managers in a with statement to apply restrictions in a rule or query conditionally. In a with statement, Python calls the context manager’s .__enter__() method before executing the with block. After the with block executes, the with statement automatically executes the Producer.__exit__() method.

Returns#

None.

Example#

You may use Producer objects in a with statement to set a property or Type conditionally:

import relationalai as rai

model = rai.Model("people")
Person = model.Type("Person")
Adult = model.Type("Adult")

with model.rule():
    Person.add(name="Fred", age=39)
    Person.add(name="Wilma", age=36)
    Person.add(name="Pebbles", age=6)

# People who 18 years old or older are adults.
with model.rule():
    person = Person()
    with person.age >= 18:
        person.set(Adult)

with model.query() as select:
    adult = Adult()
    response = select(adult.name, adult.age)

print(response.results)
# Output:
#     name  age
# 0   Fred   39
# 1  Wilma   36

The with person.age >= 18 block temporarily restricts person.age to values greater than or equal to 18. After Python executes the with block, the Producer.__exit__() method is called to remove the restriction. This allows you to write multiple conditional with statements in the same rule or query:

Child = model.Type("Child")

with model.rule():
    person = Person()
    with person.age >= 18:
        person.set(Adult)
    with person.age < 18:
        person.set(Child)

with model.query() as select:
    child = Child()
    response = select(child.name, child.age)

print(response.results)
# Output:
#       name  age
# 0  Pebbles    6

See Also#