Haverscript

Haverscript is a lightweight Python library designed to manage LLM interactions, built on top of Ollama, and its Python API. Haverscript streamlines LLM interactions by focusing on immutability, automating retries, and utilizing SQLite caching. This ensures efficient, reliable, and repeatable outcomes while reducing the complexity of managing LLM workflows.

First Example

Here’s a basic example demonstrating how to use Haverscript, with the mistral model.

from haverscript import connect
session = connect("mistral").echo()
session = session.chat("In one sentence, why is the sky blue?")
session = session.chat("Rewrite the above sentence in the style of Yoda")
session = session.chat("How many questions did I ask?")

This will give the following output.

> In one sentence, why is the sky blue?

The sky appears blue due to scattering of shorter wavelengths (blue and violet)
more than other colors by the atmosphere when sunlight enters it.

> Rewrite the above sentence in the style of Yoda

In the atmosphere, scattering of blue and violet light, more abundant, is.
This explains why sky looks blue to our eyes.

> How many questions did I ask?

You asked three questions in total: one about the reason for the blue color of the
sky, another asking me to rewrite that answer in the style of Yoda, and a third
confirming how many questions you had asked.

The examples directory contains several examples.

The DSL Design page compares Haverscript to other LLM APIs, and gives rationale behind the design.

Installing Haverscript

Haverscript is available on GitHub: https://github.com/andygill/haverscript. While it is currently in alpha and considered experimental, it is ready to use out of the box.

Prerequisites

You need to have Ollama already installed, or have access to an an Ollama compatible API end-point.

Installation

You can install Haverscript directly from the GitHub repository using pip.

Here's how to set up Haverscript:

1. First, create and activate a Python virtual environment if you haven’t already:

python3 -m venv venv
source venv/bin/activate  # On Windows: .\venv\Scripts\activate

2. Install Haverscript directly from the GitHub repository:

pip install git+https://github.com/andygill/haverscript.git@v0.1.0

In the future, if there’s enough interest, I plan to push Haverscript to PyPI for easier installation.

Documentation

The chat Method

The chat method is the main function available in both the Model and Response classes (with Response inheriting it from Model):

@dataclass(frozen=True)
class Model:
    ...
    def chat(self, prompt: str) -> Response:

@dataclass(frozen=True)
class Response(Model):
    ...

Key points:

• Immutability: Both Model and Response are immutable data structures, making them safe to share across threads or processes without concern for side effects.

• Chat Method: The chat method accepts a simple Python string as input, which can include f-strings for formatted and dynamic prompts.

  Example:

  def example(client: Model, txt: str):
      client.chat(
          f"""
          Help me understand what is happening here.
          
          {txt}
          """
      )

• Automatic Outdenting: To accommodate common formatting practices where chat is called with multi-line literal strings (often indented), the "docstrings" algorithm is applied to remove unnecessary whitespace from the prompt. You can disable this by setting the raw option before calling chat.

The Response Class

The result of a chat call is a Response. This class contains several useful attributes and defines a __str__ method for convenient string representation.

class Response(Model):
    prompt: str
    reply: str
    parent: Model

    def __str__(self):
        return self.reply
    ...

Key Points:

• Accessing the Reply: You can directly access the reply attribute to retrieve the text of the Response, or simply call str(response) for the same effect.

• String Representation: The __str__ method returns the reply attribute, so whenever a Response object is used inside an f-string, it automatically resolves to the text of the reply. (This is standard Python behavior.)

  For and example, see Chaining answers together

• str and repr: The design of the str method in Haverscript is intentional. It allows you to seamlessly include responses directly in f-strings. If you need to inspect more detailed information or structure, you can use repr or dataclasses.asdict.

The Model Class

The connect(...) function is the main entry point of the library, allowing you to create and access an initial model. This function always requires a model name and can optionally accept a hostname (which is typically omitted when running Ollama locally).

def connect(modelname: str, hostname: str = None):
    ...

To create and use a model, follow the idiomatic approach of naming the model and then using that name:

from haverscript import connect
model = connect("mistral")
response = model.chat("In one sentence, why is the sky blue?")
print(f"Response: {response}")

You can create multiple models, including duplicates of the same model, without any issues. No external actions are triggered until the chat method is called; the external connect is deferred until needed.

Setting Parameters

How do we modify a Model or Response if everything is immutable? Instead of modifying them directly, we create new versions with the desired changes, following the principles of functional programming. Helper methods make it easy to create updated versions of these objects while preserving immutability.

class Model:
    ...
    def echo(self, echo: bool = True, colorize: Optional[str] = None, width: int = 78) -> Self:
        """Echo prompts and responses to stdout."""

    def cache(self, filename: Optional[str] = None):
        """Set the cache filename for this model."""

    def system(self, prompt: str) -> Self:
        """Add a system prompt."""

    def json(self, json: bool = True) -> Self:
        """Request a JSON result."""

    def options(self, **kwargs) -> Self:
        """Set additional options for the model, like temperature and seed."""

These methods can be called on both Model and Response, returning a new instance of the same type with the specified attributes updated.

For examples, see

• System prompt in tree of calls,
• enabling the cache,
• JSON output in checking output, and
• setting ollama options.

Chaining calls

There are two primary ways to use chat:

Chaining responses

graph LR

    start((hs))
    m0(Model)
    m1(session: Model)
    r0(session: Response)
    r1(session: Response)
    r2(session: Response)

    start -- model('…') --> m0
    m0 -- echo() --> m1
    m1 -- chat('…') --> r0
    r0 -- chat('…') --> r1
    r1 -- chat('…') --> r2

    style m0 fill:none, stroke: none

Loading

This follows the typical behavior of a chat session: using the output of one chat call as the input for the next. For more details, refer to the first example.

Multiple independent calls

graph LR

    start((hs))
    m0(Model)
    m1(**session**: Model)
    r0(Response)
    r1(Response)
    r2(Response)

    start -- model('…') --> m0
    m0 -- echo() --> m1
    m1 -- chat('…') --> r0
    m1 -- chat('…') --> r1
    m1 -- chat('…') --> r2

    style m0 fill:none, stroke: none

Loading

Call chat multiple times with the same client instance to process different prompts separately. This way intentually loses the chained context, but in some cases you want to play a different persona, or do not allow the previous reply to cloud the next request. See tree of calls for an example.

Post-conditions

A Response can have post-conditions added using the check method.

class Response(Model):
    ...
    def check(self, predicate) -> Self:
        """Verify that a predicate is true, and if not, rerun the prompt."""

For example, you might use check to verify that an output is formatted correctly. Calls to check can be chained, and all post-conditions must be satisfied for the process to continue.

There are three predicate functions provided:

from haverscript import fresh, accept, valid_json

  response.check(fresh)  # Ensures the response is freshly generated (not cached).
  response.check(accept)  # Asks the user to confirm if the response is acceptable.
  response.check(valid_json)  # Check to see if the response reply is valid JSON.

For examples, see post-conditions.

FAQ

Q: How do I make the context window larger to (say) 16K?

A: set the num_ctx option.

model = model.options(num_ctx=16 * 1024)

Q: What is "haver"?

A: It's a Scottish term that means to talk aimlessly or without necessarily making sense.

Generative AI Usage

Generative AI was used as a tool to help with code authoring and documentation writing.

Future Plans

Models

• Add support for the OpenAI API, and other APIs.
• Introduce pseudo-models for tasks such as random selection.

External Artifacts

• Enable image input for multi-modal models during chats.
• Provide an API for LLM-based function calls.
• Incorporate Retrieval-Augmented Generation (RAG) capabilities.

Interface

• Develop a gradio interface for replaying scripts and monitoring LLM usage.

LLM Hacking

• Implement context compression and support for rewriting conversation histories.