---
title: Function Calling Program for Structured Extraction
 | LlamaIndex OSS Documentation
---

[![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/run-llama/llama_index/blob/main/docs/examples/output_parsing/function_program.ipynb)

This guide shows you how to do structured data extraction with our `FunctionCallingProgram`. Given a function-calling LLM as well as an output Pydantic class, generate a structured Pydantic object. We use three different function calling LLMs:

- OpenAI
- Anthropic Claude
- Mistral

In terms of the target object, you can choose to directly specify `output_cls`, or specify a `PydanticOutputParser` or any other BaseOutputParser that generates a Pydantic object.

in the examples below, we show you different ways of extracting into the `Album` object (which can contain a list of Song objects).

**NOTE**: The `FunctionCallingProgram` only works with LLMs that natively support function calling, by inserting the schema of the Pydantic object as the “tool parameters” for a tool. For all other LLMs, please use our `LLMTextCompletionProgram`, which will directly prompt the model through text to get back a structured output.

## Define `Album` class

This is a simple example of parsing an output into an `Album` schema, which can contain multiple songs.

Just pass `Album` into the `output_cls` property on initialization of the `FunctionCallingProgram`.

If you’re opening this Notebook on colab, you will probably need to install LlamaIndex 🦙.

```
!pip install llama-index
```

```
from pydantic import BaseModel
from typing import List


from llama_index.core.program import FunctionCallingProgram
```

Define output schema

```
class Song(BaseModel):
    """Data model for a song."""


    title: str
    length_seconds: int




class Album(BaseModel):
    """Data model for an album."""


    name: str
    artist: str
    songs: List[Song]
```

## Define Function Calling Program

We define a function calling program with three function-calling LLMs:

- OpenAI
- Anthropic
- Mistral

### Function Calling Program with OpenAI

Here we use gpt-3.5-turbo.

We demonstrate structured data extraction “single” function calling and also parallel function calling, allowing us to extract out multiple objects.

#### Function Calling (Single Object)

```
from llama_index.core.program import FunctionCallingProgram
from llama_index.llms.openai import OpenAI
```

```
prompt_template_str = """\
Generate an example album, with an artist and a list of songs. \
Using the movie {movie_name} as inspiration.\
"""
llm = OpenAI(model="gpt-3.5-turbo")


program = FunctionCallingProgram.from_defaults(
    output_cls=Album,
    prompt_template_str=prompt_template_str,
    verbose=True,
)
```

Run program to get structured output.

```
output = program(movie_name="The Shining")
```

```
=== Calling Function ===
Calling function: Album with args: {"name": "The Shining Soundtrack", "artist": "Various Artists", "songs": [{"title": "Main Title", "length_seconds": 180}, {"title": "Rocky Mountains", "length_seconds": 240}, {"title": "Lullaby", "length_seconds": 200}, {"title": "The Overlook Hotel", "length_seconds": 220}, {"title": "Grady's Story", "length_seconds": 180}, {"title": "The Maze", "length_seconds": 210}]}
=== Function Output ===
name='The Shining Soundtrack' artist='Various Artists' songs=[Song(title='Main Title', length_seconds=180), Song(title='Rocky Mountains', length_seconds=240), Song(title='Lullaby', length_seconds=200), Song(title='The Overlook Hotel', length_seconds=220), Song(title="Grady's Story", length_seconds=180), Song(title='The Maze', length_seconds=210)]
```

The output is a valid Pydantic object that we can then use to call functions/APIs.

```
output
```

```
Album(name='The Shining Soundtrack', artist='Various Artists', songs=[Song(title='Main Title', length_seconds=180), Song(title='Rocky Mountains', length_seconds=240), Song(title='Lullaby', length_seconds=200), Song(title='The Overlook Hotel', length_seconds=220), Song(title="Grady's Story", length_seconds=180), Song(title='The Maze', length_seconds=210)])
```

#### Function Calling (Parallel Function Calling, Multiple Objects)

```
prompt_template_str = """\
Generate example albums, with an artist and a list of songs, using each movie below as inspiration. \


Here are the movies:
{movie_names}
"""
llm = OpenAI(model="gpt-3.5-turbo")


program = FunctionCallingProgram.from_defaults(
    output_cls=Album,
    prompt_template_str=prompt_template_str,
    verbose=True,
    allow_parallel_tool_calls=True,
)
output = program(movie_names="The Shining, The Blair Witch Project, Saw")
```

```
=== Calling Function ===
Calling function: Album with args: {"name": "The Shining", "artist": "Various Artists", "songs": [{"title": "Main Theme", "length_seconds": 180}, {"title": "The Overlook Hotel", "length_seconds": 240}, {"title": "Redrum", "length_seconds": 200}]}
=== Function Output ===
name='The Shining' artist='Various Artists' songs=[Song(title='Main Theme', length_seconds=180), Song(title='The Overlook Hotel', length_seconds=240), Song(title='Redrum', length_seconds=200)]
=== Calling Function ===
Calling function: Album with args: {"name": "The Blair Witch Project", "artist": "Soundtrack Ensemble", "songs": [{"title": "Into the Woods", "length_seconds": 210}, {"title": "The Rustling Leaves", "length_seconds": 180}, {"title": "The Witch's Curse", "length_seconds": 240}]}
=== Function Output ===
name='The Blair Witch Project' artist='Soundtrack Ensemble' songs=[Song(title='Into the Woods', length_seconds=210), Song(title='The Rustling Leaves', length_seconds=180), Song(title="The Witch's Curse", length_seconds=240)]
=== Calling Function ===
Calling function: Album with args: {"name": "Saw", "artist": "Horror Soundscapes", "songs": [{"title": "The Reverse Bear Trap", "length_seconds": 220}, {"title": "Jigsaw's Game", "length_seconds": 260}, {"title": "Bathroom Escape", "length_seconds": 180}]}
=== Function Output ===
name='Saw' artist='Horror Soundscapes' songs=[Song(title='The Reverse Bear Trap', length_seconds=220), Song(title="Jigsaw's Game", length_seconds=260), Song(title='Bathroom Escape', length_seconds=180)]
```

```
output
```

```
[Album(name='The Shining', artist='Various Artists', songs=[Song(title='Main Theme', length_seconds=180), Song(title='The Overlook Hotel', length_seconds=240), Song(title='Redrum', length_seconds=200)]),
 Album(name='The Blair Witch Project', artist='Soundtrack Ensemble', songs=[Song(title='Into the Woods', length_seconds=210), Song(title='The Rustling Leaves', length_seconds=180), Song(title="The Witch's Curse", length_seconds=240)]),
 Album(name='Saw', artist='Horror Soundscapes', songs=[Song(title='The Reverse Bear Trap', length_seconds=220), Song(title="Jigsaw's Game", length_seconds=260), Song(title='Bathroom Escape', length_seconds=180)])]
```

### Function Calling Program with Anthropic

Here we use Claude Sonnet (all three models support function calling).

```
from llama_index.core.program import FunctionCallingProgram
from llama_index.llms.anthropic import Anthropic
```

```
prompt_template_str = "Generate a song about {topic}."
llm = Anthropic(model="claude-3-sonnet-20240229")


program = FunctionCallingProgram.from_defaults(
    output_cls=Song,
    prompt_template_str=prompt_template_str,
    llm=llm,
    verbose=True,
)
```

```
output = program(topic="harry potter")
```

```
=== Calling Function ===
Calling function: Song with args: {"title": "The Boy Who Lived", "length_seconds": 180}
=== Function Output ===
title='The Boy Who Lived' length_seconds=180
```

```
output
```

```
Song(title='The Boy Who Lived', length_seconds=180)
```

### Function Calling Program with Mistral

Here we use mistral-large.

```
from llama_index.core.program import FunctionCallingProgram
from llama_index.llms.mistralai import MistralAI
```

```
# prompt_template_str = """\
# Generate an example album, with an artist and a list of songs. \
# Use the broadway show {broadway_show} as inspiration. \
# Make sure to use the tool.
# """
prompt_template_str = "Generate a song about {topic}."
llm = MistralAI(model="mistral-large-latest")
program = FunctionCallingProgram.from_defaults(
    output_cls=Song,
    prompt_template_str=prompt_template_str,
    llm=llm,
    verbose=True,
)
```

```
output = program(topic="the broadway show Wicked")
```

```
=== Calling Function ===
Calling function: Song with args: {"title": "Defying Gravity", "length_seconds": 240}
=== Function Output ===
title='Defying Gravity' length_seconds=240
```

```
output
```

```
Song(title='Defying Gravity', length_seconds=240)
```

```
from llama_index.core.output_parsers import PydanticOutputParser


program = LLMTextCompletionProgram.from_defaults(
    output_parser=PydanticOutputParser(output_cls=Album),
    prompt_template_str=prompt_template_str,
    verbose=True,
)
```

```
output = program(movie_name="Lord of the Rings")
output
```

```
Album(name='The Fellowship of the Ring', artist='Middle-earth Ensemble', songs=[Song(title='The Shire', length_seconds=240), Song(title='Concerning Hobbits', length_seconds=180), Song(title='The Ring Goes South', length_seconds=300), Song(title='A Knife in the Dark', length_seconds=270), Song(title='Flight to the Ford', length_seconds=210), Song(title='Many Meetings', length_seconds=240), Song(title='The Council of Elrond', length_seconds=330), Song(title='The Great Eye', length_seconds=180), Song(title='The Breaking of the Fellowship', length_seconds=360)])
```