🗒️ Structured outputs for LLMs 🗒️

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Table of Contents

• Why Outlines?
• Quickstart
• Real-World Examples
  • 🙋‍♂️ Customer Support Triage
  • 📦 E-commerce Product Categorization
  • 📊 Parse Event Details with Incomplete Data
  • 🗂️ Categorize Documents into Predefined Types
  • 📅 Schedule a Meeting with Function Calling
  • 📝 Dynamically Generate Prompts with Re-usable Templates
• They Use Outlines
• Model Integrations
• Core Features
• Other Features
• About .txt
• Community

Why Outlines?

LLMs are powerful but their outputs are unpredictable. Most solutions attempt to fix bad outputs after generation using parsing, regex, or fragile code that breaks easily.

Outlines guarantees structured outputs during generation — directly from any LLM.

• Works with any model - Same code runs across OpenAI, Ollama, vLLM, and more
• Simple integration - Just pass your desired output type: model(prompt, output_type)
• Guaranteed valid structure - No more parsing headaches or broken JSON
• Provider independence - Switch models without changing code

The Outlines Philosophy

Outlines follows a simple pattern that mirrors Python's own type system. Simply specify the desired output type, and Outlines will ensure your data matches that structure exactly:

• For a yes/no response, use Literal["Yes", "No"]
• For numerical values, use int
• For complex objects, define a structure with a Pydantic model

Quickstart

Getting started with outlines is simple:

1. Install outlines

pip install outlines

2. Connect to your preferred model

import outlines
from transformers import AutoTokenizer, AutoModelForCausalLM


MODEL_NAME = "microsoft/Phi-3-mini-4k-instruct"
model = outlines.from_transformers(
    AutoModelForCausalLM.from_pretrained(MODEL_NAME, device_map="auto"),
    AutoTokenizer.from_pretrained(MODEL_NAME)
)

3. Start with simple structured outputs

from typing import Literal
from pydantic import BaseModel


# Simple classification
sentiment = model(
    "Analyze: 'This product completely changed my life!'",
    Literal["Positive", "Negative", "Neutral"]
)
print(sentiment)  # "Positive"

# Extract specific types
temperature = model("What's the boiling point of water in Celsius?", int)
print(temperature)  # 100

4. Create complex structures

from pydantic import BaseModel
from enum import Enum

class Rating(Enum):
    poor = 1
    fair = 2
    good = 3
    excellent = 4

class ProductReview(BaseModel):
    rating: Rating
    pros: list[str]
    cons: list[str]
    summary: str

review = model(
    "Review: The XPS 13 has great battery life and a stunning display, but it runs hot and the webcam is poor quality.",
    ProductReview,
    max_new_tokens=200,
)

review = ProductReview.model_validate_json(review)
print(f"Rating: {review.rating.name}")  # "Rating: good"
print(f"Pros: {review.pros}")           # "Pros: ['great battery life', 'stunning display']"
print(f"Summary: {review.summary}")     # "Summary: Good laptop with great display but thermal issues"

Real-world examples

Here are production-ready examples showing how Outlines solves common problems:

import outlines
from enum import Enum
from pydantic import BaseModel
from transformers import AutoTokenizer, AutoModelForCausalLM
from typing import List


MODEL_NAME = "microsoft/Phi-3-mini-4k-instruct"
model = outlines.from_transformers(
    AutoModelForCausalLM.from_pretrained(MODEL_NAME, device_map="auto"),
    AutoTokenizer.from_pretrained(MODEL_NAME)
)


def alert_manager(ticket):
    print("Alert!", ticket)


class TicketPriority(str, Enum):
    low = "low"
    medium = "medium"
    high = "high"
    urgent = "urgent"

class ServiceTicket(BaseModel):
    priority: TicketPriority
    category: str
    requires_manager: bool
    summary: str
    action_items: List[str]


customer_email = """
Subject: URGENT - Cannot access my account after payment

I paid for the premium plan 3 hours ago and still can't access any features.
I've tried logging out and back in multiple times. This is unacceptable as I
have a client presentation in an hour and need the analytics dashboard.
Please fix this immediately or refund my payment.
"""

prompt = f"""
<|im_start|>user
Analyze this customer email:

{customer_email}
<|im_end|>
<|im_start|>assistant
"""

ticket = model(
    prompt,
    ServiceTicket,
    max_new_tokens=500
)

# Use structured data to route the ticket
ticket = ServiceTicket.model_validate_json(ticket)
if ticket.priority == "urgent" or ticket.requires_manager:
    alert_manager(ticket)

import outlines
from pydantic import BaseModel
from transformers import AutoTokenizer, AutoModelForCausalLM
from typing import List, Optional


MODEL_NAME = "microsoft/Phi-3-mini-4k-instruct"
model = outlines.from_transformers(
    AutoModelForCausalLM.from_pretrained(MODEL_NAME, device_map="auto"),
    AutoTokenizer.from_pretrained(MODEL_NAME)
)


def update_inventory(product, category, sub_category):
    print(f"Updated {product.split(',')[0]} in category {category}/{sub_category}")


class ProductCategory(BaseModel):
    main_category: str
    sub_category: str
    attributes: List[str]
    brand_match: Optional[str]

# Process product descriptions in batches
product_descriptions = [
    "Apple iPhone 15 Pro Max 256GB Titanium, 6.7-inch Super Retina XDR display with ProMotion",
    "Organic Cotton T-Shirt, Men's Medium, Navy Blue, 100% Sustainable Materials",
    "KitchenAid Stand Mixer, 5 Quart, Red, 10-Speed Settings with Dough Hook Attachment"
]

template = outlines.Template.from_string("""
<|im_start|>user
Categorize this product:

{{ description }}
<|im_end|>
<|im_start|>assistant
""")

# Get structured categorization for all products
categories = model(
    [template(description=desc) for desc in product_descriptions],
    ProductCategory,
    max_new_tokens=200
)

# Use categorization for inventory management
categories = [
    ProductCategory.model_validate_json(category) for category in categories
]
for product, category in zip(product_descriptions, categories):
    update_inventory(product, category.main_category, category.sub_category)