# StreamlitCallbackHandler

> **Class** in `langchain_community`

📖 [View in docs](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler)

Callback handler that writes to a Streamlit app.

## Signature

```python
StreamlitCallbackHandler(
    self,
    parent_container: DeltaGenerator,
    *,
    max_thought_containers: int = 4,
    expand_new_thoughts: bool = True,
    collapse_completed_thoughts: bool = True,
    thought_labeler: Optional[LLMThoughtLabeler] = None,
)
```

## Extends

- `BaseCallbackHandler`

## Constructors

```python
__init__(
    self,
    parent_container: DeltaGenerator,
    *,
    max_thought_containers: int = 4,
    expand_new_thoughts: bool = True,
    collapse_completed_thoughts: bool = True,
    thought_labeler: Optional[LLMThoughtLabeler] = None,
)
```

| Name | Type |
|------|------|
| `parent_container` | `DeltaGenerator` |
| `max_thought_containers` | `int` |
| `expand_new_thoughts` | `bool` |
| `collapse_completed_thoughts` | `bool` |
| `thought_labeler` | `Optional[LLMThoughtLabeler]` |


## Methods

- [`on_llm_start()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_llm_start)
- [`on_llm_new_token()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_llm_new_token)
- [`on_llm_end()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_llm_end)
- [`on_llm_error()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_llm_error)
- [`on_tool_start()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_tool_start)
- [`on_tool_end()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_tool_end)
- [`on_tool_error()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_tool_error)
- [`on_text()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_text)
- [`on_chain_start()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_chain_start)
- [`on_chain_end()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_chain_end)
- [`on_chain_error()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_chain_error)
- [`on_agent_action()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_agent_action)
- [`on_agent_finish()`](https://reference.langchain.com/python/langchain-community/callbacks/streamlit/streamlit_callback_handler/StreamlitCallbackHandler/on_agent_finish)

---

[View source on GitHub](https://github.com/langchain-ai/langchain-community/blob/a6a6079511ac8a5c1293337f88096b8641562e77/libs/community/langchain_community/callbacks/streamlit/streamlit_callback_handler.py#L231)