Types & Pydantic Integration

OpenHosta natively supports Python's typing modules and Pydantic V2 definitions out-of-the-box.

Supported Types

You can use standard Python types as the return type for an emulate function. Supported types include List, Dict, Tuple, Set, FrozenSet, Deque, Iterable, Sequence, Mapping, Union, Optional, and Literal.

Supported built-in types include int, float, str, bool.

Starting from OpenHosta 4.1, you can also return executable code using Callable.

See Generative Functions & Callable for more details.

from OpenHosta import emulate
from typing import Dict, Tuple, List

def analyze_text(text: str) -> Dict[str, List[Tuple[int, str]]]:
    """Analyze text to map each word to a list of tuples containing word length and word."""
    return emulate()

analysis = analyze_text("Hello, World!")

Pydantic Output Validation

The most deterministic way to control the output structure is using Pydantic. OpenHosta will format the prompt to request JSON that matches the Pydantic schema and then cast the resulting JSON back into Pydantic models.

from pydantic import BaseModel
from OpenHosta import emulate

class Person(BaseModel):
    name: str
    age: int

def find_first_name(sentence: str) -> Person:
    """Finds the name and age of a person in the text."""
    return emulate()

print(find_first_name("The captain's age is one year more than the first officer's age. The first officer is 30 years old"))
# Person(name='first officer', age=30)

Guarded Types

In OpenHosta V4, Guarded Types provide a robust abstraction for ensuring type structural and semantic validitiy behind the scenes. This handles strict validation rules during extraction pipelines.

See Guarded Types Overview for more details.