astream_events() — langchain Function Reference
Architecture documentation for the astream_events() function in base.py from the langchain codebase.
Entity Profile
Dependency Diagram
graph TD 67cad9a2_ee89_d44e_40ab_e55a36396c0d["astream_events()"] 4a62481c_02cb_a5de_1833_50669d5351a6["Runnable"] 67cad9a2_ee89_d44e_40ab_e55a36396c0d -->|defined in| 4a62481c_02cb_a5de_1833_50669d5351a6 587028d9_69c4_7ed8_45fe_d86e3f085696["astream_events()"] 587028d9_69c4_7ed8_45fe_d86e3f085696 -->|calls| 67cad9a2_ee89_d44e_40ab_e55a36396c0d 587028d9_69c4_7ed8_45fe_d86e3f085696["astream_events()"] 67cad9a2_ee89_d44e_40ab_e55a36396c0d -->|calls| 587028d9_69c4_7ed8_45fe_d86e3f085696 e2bea970_c5e9_9585_6fa1_e85a5a79ce5e["with_config()"] 67cad9a2_ee89_d44e_40ab_e55a36396c0d -->|calls| e2bea970_c5e9_9585_6fa1_e85a5a79ce5e style 67cad9a2_ee89_d44e_40ab_e55a36396c0d fill:#6366f1,stroke:#818cf8,color:#fff
Relationship Graph
Source Code
libs/core/langchain_core/runnables/base.py lines 1273–1517
async def astream_events(
self,
input: Any,
config: RunnableConfig | None = None,
*,
version: Literal["v1", "v2"] = "v2",
include_names: Sequence[str] | None = None,
include_types: Sequence[str] | None = None,
include_tags: Sequence[str] | None = None,
exclude_names: Sequence[str] | None = None,
exclude_types: Sequence[str] | None = None,
exclude_tags: Sequence[str] | None = None,
**kwargs: Any,
) -> AsyncIterator[StreamEvent]:
"""Generate a stream of events.
Use to create an iterator over `StreamEvent` that provide real-time information
about the progress of the `Runnable`, including `StreamEvent` from intermediate
results.
A `StreamEvent` is a dictionary with the following schema:
- `event`: Event names are of the format:
`on_[runnable_type]_(start|stream|end)`.
- `name`: The name of the `Runnable` that generated the event.
- `run_id`: Randomly generated ID associated with the given execution of the
`Runnable` that emitted the event. A child `Runnable` that gets invoked as
part of the execution of a parent `Runnable` is assigned its own unique ID.
- `parent_ids`: The IDs of the parent runnables that generated the event. The
root `Runnable` will have an empty list. The order of the parent IDs is from
the root to the immediate parent. Only available for v2 version of the API.
The v1 version of the API will return an empty list.
- `tags`: The tags of the `Runnable` that generated the event.
- `metadata`: The metadata of the `Runnable` that generated the event.
- `data`: The data associated with the event. The contents of this field
depend on the type of event. See the table below for more details.
Below is a table that illustrates some events that might be emitted by various
chains. Metadata fields have been omitted from the table for brevity.
Chain definitions have been included after the table.
!!! note
This reference table is for the v2 version of the schema.
| event | name | chunk | input | output |
| ---------------------- | -------------------- | ----------------------------------- | ------------------------------------------------- | --------------------------------------------------- |
| `on_chat_model_start` | `'[model name]'` | | `{"messages": [[SystemMessage, HumanMessage]]}` | |
| `on_chat_model_stream` | `'[model name]'` | `AIMessageChunk(content="hello")` | | |
| `on_chat_model_end` | `'[model name]'` | | `{"messages": [[SystemMessage, HumanMessage]]}` | `AIMessageChunk(content="hello world")` |
| `on_llm_start` | `'[model name]'` | | `{'input': 'hello'}` | |
| `on_llm_stream` | `'[model name]'` | `'Hello' ` | | |
| `on_llm_end` | `'[model name]'` | | `'Hello human!'` | |
| `on_chain_start` | `'format_docs'` | | | |
| `on_chain_stream` | `'format_docs'` | `'hello world!, goodbye world!'` | | |
| `on_chain_end` | `'format_docs'` | | `[Document(...)]` | `'hello world!, goodbye world!'` |
| `on_tool_start` | `'some_tool'` | | `{"x": 1, "y": "2"}` | |
| `on_tool_end` | `'some_tool'` | | | `{"x": 1, "y": "2"}` |
| `on_retriever_start` | `'[retriever name]'` | | `{"query": "hello"}` | |
| `on_retriever_end` | `'[retriever name]'` | | `{"query": "hello"}` | `[Document(...), ..]` |
| `on_prompt_start` | `'[template_name]'` | | `{"question": "hello"}` | |
| `on_prompt_end` | `'[template_name]'` | | `{"question": "hello"}` | `ChatPromptValue(messages: [SystemMessage, ...])` |
In addition to the standard events, users can also dispatch custom events (see example below).
Custom events will be only be surfaced with in the v2 version of the API!
A custom event has following format:
| Attribute | Type | Description |
| ----------- | ------ | --------------------------------------------------------------------------------------------------------- |
| `name` | `str` | A user defined name for the event. |
| `data` | `Any` | The data associated with the event. This can be anything, though we suggest making it JSON serializable. |
Here are declarations associated with the standard events shown above:
`format_docs`:
```python
def format_docs(docs: list[Document]) -> str:
'''Format the docs.'''
return ", ".join([doc.page_content for doc in docs])Domain
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Defined In
Called By
Source
Frequently Asked Questions
What does astream_events() do?
astream_events() is a function in the langchain codebase, defined in libs/core/langchain_core/runnables/base.py.
Where is astream_events() defined?
astream_events() is defined in libs/core/langchain_core/runnables/base.py at line 1273.
What does astream_events() call?
astream_events() calls 2 function(s): astream_events, with_config.
What calls astream_events()?
astream_events() is called by 1 function(s): astream_events.
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