使用函数式 API¶

函数式 API (Functional API) 允许您在现有代码上进行最小改动，即可将 LangGraph 的核心功能——持久化、记忆、人在回路和流式传输——添加到您的应用程序中。

提示

有关函数式 API 的概念信息，请参阅函数式 API。

创建简单工作流¶

定义 entrypoint 时，输入仅限于函数的第一个参数。要传递多个输入，可以使用字典。

@entrypoint(checkpointer=checkpointer)
def my_workflow(inputs: dict) -> int:
    value = inputs["value"]
    another_value = inputs["another_value"]
    ...

my_workflow.invoke({"value": 1, "another_value": 2})

扩展示例：简单工作流

import uuid
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import MemorySaver

# Task that checks if a number is even
@task
def is_even(number: int) -> bool:
    return number % 2 == 0

# Task that formats a message
@task
def format_message(is_even: bool) -> str:
    return "The number is even." if is_even else "The number is odd."

# Create a checkpointer for persistence
checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def workflow(inputs: dict) -> str:
    """Simple workflow to classify a number."""
    even = is_even(inputs["number"]).result()
    return format_message(even).result()

# Run the workflow with a unique thread ID
config = {"configurable": {"thread_id": str(uuid.uuid4())}}
result = workflow.invoke({"number": 7}, config=config)
print(result)

扩展示例：用 LLM 撰写文章

本示例演示了如何从语法上使用 @task 和 @entrypoint 装饰器。如果提供了检查点，工作流结果将持久化到检查点中。

import uuid
from langchain.chat_models import init_chat_model
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import MemorySaver

llm = init_chat_model('openai:gpt-3.5-turbo')

# Task: generate essay using an LLM
@task
def compose_essay(topic: str) -> str:
    """Generate an essay about the given topic."""
    return llm.invoke([
        {"role": "system", "content": "You are a helpful assistant that writes essays."},
        {"role": "user", "content": f"Write an essay about {topic}."}
    ]).content

# Create a checkpointer for persistence
checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def workflow(topic: str) -> str:
    """Simple workflow that generates an essay with an LLM."""
    return compose_essay(topic).result()

# Execute the workflow
config = {"configurable": {"thread_id": str(uuid.uuid4())}}
result = workflow.invoke("the history of flight", config=config)
print(result)

并行执行¶

任务可以通过并发调用并等待结果来并行执行。这对于提高 I/O 密集型任务（例如，调用 LLM 的 API）的性能非常有用。

@task
def add_one(number: int) -> int:
    return number + 1

@entrypoint(checkpointer=checkpointer)
def graph(numbers: list[int]) -> list[str]:
    futures = [add_one(i) for i in numbers]
    return [f.result() for f in futures]

扩展示例：并行 LLM 调用

此示例演示了如何使用 @task 并行运行多个 LLM 调用。每个调用生成一个关于不同主题的段落，结果合并为单个文本输出。

import uuid
from langchain.chat_models import init_chat_model
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import MemorySaver

# Initialize the LLM model
llm = init_chat_model("openai:gpt-3.5-turbo")

# Task that generates a paragraph about a given topic
@task
def generate_paragraph(topic: str) -> str:
    response = llm.invoke([
        {"role": "system", "content": "You are a helpful assistant that writes educational paragraphs."},
        {"role": "user", "content": f"Write a paragraph about {topic}."}
    ])
    return response.content

# Create a checkpointer for persistence
checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def workflow(topics: list[str]) -> str:
    """Generates multiple paragraphs in parallel and combines them."""
    futures = [generate_paragraph(topic) for topic in topics]
    paragraphs = [f.result() for f in futures]
    return "\n\n".join(paragraphs)

# Run the workflow
config = {"configurable": {"thread_id": str(uuid.uuid4())}}
result = workflow.invoke(["quantum computing", "climate change", "history of aviation"], config=config)
print(result)

此示例使用 LangGraph 的并发模型来提高执行时间，尤其是在任务涉及 I/O（如 LLM 完成）时。

调用图¶

函数式 API 和图 API 可以在同一个应用程序中一起使用，因为它们共享相同的底层运行时。

^{API 参考：entrypoint | StateGraph}

from langgraph.func import entrypoint
from langgraph.graph import StateGraph

builder = StateGraph()
...
some_graph = builder.compile()

@entrypoint()
def some_workflow(some_input: dict) -> int:
    # Call a graph defined using the graph API
    result_1 = some_graph.invoke(...)
    # Call another graph defined using the graph API
    result_2 = another_graph.invoke(...)
    return {
        "result_1": result_1,
        "result_2": result_2
    }

扩展示例：从函数式 API 调用一个简单图

import uuid
from typing import TypedDict
from langgraph.func import entrypoint
from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph import StateGraph

# Define the shared state type
class State(TypedDict):
    foo: int

# Define a simple transformation node
def double(state: State) -> State:
    return {"foo": state["foo"] * 2}

# Build the graph using the Graph API
builder = StateGraph(State)
builder.add_node("double", double)
builder.set_entry_point("double")
graph = builder.compile()

# Define the functional API workflow
checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def workflow(x: int) -> dict:
    result = graph.invoke({"foo": x})
    return {"bar": result["foo"]}

# Execute the workflow
config = {"configurable": {"thread_id": str(uuid.uuid4())}}
print(workflow.invoke(5, config=config))  # Output: {'bar': 10}

调用其他入口点¶

您可以从一个 entrypoint 或一个 task 中调用其他 entrypoint。

@entrypoint() # Will automatically use the checkpointer from the parent entrypoint
def some_other_workflow(inputs: dict) -> int:
    return inputs["value"]

@entrypoint(checkpointer=checkpointer)
def my_workflow(inputs: dict) -> int:
    value = some_other_workflow.invoke({"value": 1})
    return value

扩展示例：调用另一个入口点

import uuid
from langgraph.func import entrypoint
from langgraph.checkpoint.memory import MemorySaver

# Initialize a checkpointer
checkpointer = MemorySaver()

# A reusable sub-workflow that multiplies a number
@entrypoint()
def multiply(inputs: dict) -> int:
    return inputs["a"] * inputs["b"]

# Main workflow that invokes the sub-workflow
@entrypoint(checkpointer=checkpointer)
def main(inputs: dict) -> dict:
    result = multiply.invoke({"a": inputs["x"], "b": inputs["y"]})
    return {"product": result}

# Execute the main workflow
config = {"configurable": {"thread_id": str(uuid.uuid4())}}
print(main.invoke({"x": 6, "y": 7}, config=config))  # Output: {'product': 42}

流式传输¶

函数式 API 使用与 图 API 相同的流式传输机制。更多详细信息请阅读流式传输指南部分。

使用流式 API 流式传输更新和自定义数据的示例。

^{API 参考：entrypoint | MemorySaver | get_stream_writer}

from langgraph.func import entrypoint
from langgraph.checkpoint.memory import MemorySaver
from langgraph.config import get_stream_writer # (1)!

checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def main(inputs: dict) -> int:
    writer = get_stream_writer() # (2)!
    writer("Started processing") # (3)!
    result = inputs["x"] * 2
    writer(f"Result is {result}") # (4)!
    return result

config = {"configurable": {"thread_id": "abc"}}

for mode, chunk in main.stream( # (5)!
    {"x": 5},
    stream_mode=["custom", "updates"], # (6)!
    config=config
):
    print(f"{mode}: {chunk}")

从 langgraph.config 导入 get_stream_writer。
在入口点内获取流式写入器实例。
在计算开始前发出自定义数据。
计算结果后发出另一个自定义消息。
使用 .stream() 处理流式输出。
指定要使用的流式传输模式。

('updates', {'add_one': 2})
('updates', {'add_two': 3})
('custom', 'hello')
('custom', 'world')
('updates', {'main': 5})

Python < 3.11 的异步

如果使用 Python < 3.11 且编写异步代码，则 get_stream_writer() 将无法工作。请直接使用 StreamWriter 类。有关更多详细信息，请参阅Python < 3.11 的异步。

from langgraph.types import StreamWriter

@entrypoint(checkpointer=checkpointer)
async def main(inputs: dict, writer: StreamWriter) -> int:
    ...

重试策略¶

^{API 参考：MemorySaver | entrypoint | task | RetryPolicy}

from langgraph.checkpoint.memory import MemorySaver
from langgraph.func import entrypoint, task
from langgraph.types import RetryPolicy

# This variable is just used for demonstration purposes to simulate a network failure.
# It's not something you will have in your actual code.
attempts = 0

# Let's configure the RetryPolicy to retry on ValueError.
# The default RetryPolicy is optimized for retrying specific network errors.
retry_policy = RetryPolicy(retry_on=ValueError)

@task(retry_policy=retry_policy) 
def get_info():
    global attempts
    attempts += 1

    if attempts < 2:
        raise ValueError('Failure')
    return "OK"

checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def main(inputs, writer):
    return get_info().result()

config = {
    "configurable": {
        "thread_id": "1"
    }
}

main.invoke({'any_input': 'foobar'}, config=config)

'OK'

缓存任务¶

^{API 参考：entrypoint | task}

import time
from langgraph.cache.memory import InMemoryCache
from langgraph.func import entrypoint, task
from langgraph.types import CachePolicy


@task(cache_policy=CachePolicy(ttl=120))  # (1)!
def slow_add(x: int) -> int:
    time.sleep(1)
    return x * 2


@entrypoint(cache=InMemoryCache())
def main(inputs: dict) -> dict[str, int]:
    result1 = slow_add(inputs["x"]).result()
    result2 = slow_add(inputs["x"]).result()
    return {"result1": result1, "result2": result2}


for chunk in main.stream({"x": 5}, stream_mode="updates"):
    print(chunk)

#> {'slow_add': 10}
#> {'slow_add': 10, '__metadata__': {'cached': True}}
#> {'main': {'result1': 10, 'result2': 10}}

ttl 以秒为单位指定。缓存在此时间后将失效。

错误后恢复¶

^{API 参考：MemorySaver | entrypoint | task | StreamWriter}

import time
from langgraph.checkpoint.memory import MemorySaver
from langgraph.func import entrypoint, task
from langgraph.types import StreamWriter

# This variable is just used for demonstration purposes to simulate a network failure.
# It's not something you will have in your actual code.
attempts = 0

@task()
def get_info():
    """
    Simulates a task that fails once before succeeding.
    Raises an exception on the first attempt, then returns "OK" on subsequent tries.
    """
    global attempts
    attempts += 1

    if attempts < 2:
        raise ValueError("Failure")  # Simulate a failure on the first attempt
    return "OK"

# Initialize an in-memory checkpointer for persistence
checkpointer = MemorySaver()

@task
def slow_task():
    """
    Simulates a slow-running task by introducing a 1-second delay.
    """
    time.sleep(1)
    return "Ran slow task."

@entrypoint(checkpointer=checkpointer)
def main(inputs, writer: StreamWriter):
    """
    Main workflow function that runs the slow_task and get_info tasks sequentially.

    Parameters:
    - inputs: Dictionary containing workflow input values.
    - writer: StreamWriter for streaming custom data.

    The workflow first executes `slow_task` and then attempts to execute `get_info`,
    which will fail on the first invocation.
    """
    slow_task_result = slow_task().result()  # Blocking call to slow_task
    get_info().result()  # Exception will be raised here on the first attempt
    return slow_task_result

# Workflow execution configuration with a unique thread identifier
config = {
    "configurable": {
        "thread_id": "1"  # Unique identifier to track workflow execution
    }
}

# This invocation will take ~1 second due to the slow_task execution
try:
    # First invocation will raise an exception due to the `get_info` task failing
    main.invoke({'any_input': 'foobar'}, config=config)
except ValueError:
    pass  # Handle the failure gracefully

当我们恢复执行时，无需重新运行 slow_task，因为其结果已保存在检查点中。

main.invoke(None, config=config)

'Ran slow task.'

人机协作 (Human-in-the-loop)¶

函数式 API 支持使用 interrupt 函数和 Command 原语的人在回路工作流。

基本的人在回路工作流¶

我们将创建三个任务

追加 "bar"。
暂停以等待人工输入。恢复时，追加人工输入。
追加 "qux"。

^{API 参考：entrypoint | task | Command | interrupt}

from langgraph.func import entrypoint, task
from langgraph.types import Command, interrupt


@task
def step_1(input_query):
    """Append bar."""
    return f"{input_query} bar"


@task
def human_feedback(input_query):
    """Append user input."""
    feedback = interrupt(f"Please provide feedback: {input_query}")
    return f"{input_query} {feedback}"


@task
def step_3(input_query):
    """Append qux."""
    return f"{input_query} qux"

我们现在可以在入口点中组合这些任务

^{API 参考：MemorySaver}

from langgraph.checkpoint.memory import MemorySaver

checkpointer = MemorySaver()


@entrypoint(checkpointer=checkpointer)
def graph(input_query):
    result_1 = step_1(input_query).result()
    result_2 = human_feedback(result_1).result()
    result_3 = step_3(result_2).result()

    return result_3

interrupt() 在任务内部被调用，允许人工审查和编辑前一个任务的输出。先前任务（本例中为 step_1）的结果被持久化，因此在 interrupt 之后它们不会再次运行。

让我们发送一个查询字符串

config = {"configurable": {"thread_id": "1"}}

for event in graph.stream("foo", config):
    print(event)
    print("\n")

请注意，我们在 step_1 之后通过 interrupt 暂停了。中断提供了恢复运行的指令。要恢复，我们发出一个包含 human_feedback 任务所需数据的命令。

# Continue execution
for event in graph.stream(Command(resume="baz"), config):
    print(event)
    print("\n")

恢复后，运行将继续执行剩余步骤并按预期终止。

审查工具调用¶

为了在执行前审查工具调用，我们添加了一个 review_tool_call 函数，该函数调用 interrupt。当此函数被调用时，执行将暂停，直到我们发出命令以恢复它。

给定一个工具调用，我们的函数将 interrupt 以供人工审查。此时我们可以：

接受工具调用
修改工具调用并继续
生成自定义工具消息（例如，指示模型重新格式化其工具调用）

from typing import Union

def review_tool_call(tool_call: ToolCall) -> Union[ToolCall, ToolMessage]:
    """Review a tool call, returning a validated version."""
    human_review = interrupt(
        {
            "question": "Is this correct?",
            "tool_call": tool_call,
        }
    )
    review_action = human_review["action"]
    review_data = human_review.get("data")
    if review_action == "continue":
        return tool_call
    elif review_action == "update":
        updated_tool_call = {**tool_call, **{"args": review_data}}
        return updated_tool_call
    elif review_action == "feedback":
        return ToolMessage(
            content=review_data, name=tool_call["name"], tool_call_id=tool_call["id"]
        )

我们现在可以更新入口点以审查生成的工具调用。如果工具调用被接受或修改，我们像以前一样执行。否则，我们只追加人工提供的 ToolMessage。先前任务（本例中为初始模型调用）的结果被持久化，因此在 interrupt 之后它们不会再次运行。

^{API 参考：MemorySaver | add_messages | Command | interrupt}

from langgraph.checkpoint.memory import MemorySaver
from langgraph.graph.message import add_messages
from langgraph.types import Command, interrupt


checkpointer = MemorySaver()


@entrypoint(checkpointer=checkpointer)
def agent(messages, previous):
    if previous is not None:
        messages = add_messages(previous, messages)

    llm_response = call_model(messages).result()
    while True:
        if not llm_response.tool_calls:
            break

        # Review tool calls
        tool_results = []
        tool_calls = []
        for i, tool_call in enumerate(llm_response.tool_calls):
            review = review_tool_call(tool_call)
            if isinstance(review, ToolMessage):
                tool_results.append(review)
            else:  # is a validated tool call
                tool_calls.append(review)
                if review != tool_call:
                    llm_response.tool_calls[i] = review  # update message

        # Execute remaining tool calls
        tool_result_futures = [call_tool(tool_call) for tool_call in tool_calls]
        remaining_tool_results = [fut.result() for fut in tool_result_futures]

        # Append to message list
        messages = add_messages(
            messages,
            [llm_response, *tool_results, *remaining_tool_results],
        )

        # Call model again
        llm_response = call_model(messages).result()

    # Generate final response
    messages = add_messages(messages, llm_response)
    return entrypoint.final(value=llm_response, save=messages)

短期记忆¶

短期记忆允许在同一线程 ID 的不同调用之间存储信息。有关更多详细信息，请参阅短期记忆。

管理检查点¶

您可以查看和删除检查点存储的信息。

查看线程状态（检查点）¶

config = {
    "configurable": {
        "thread_id": "1",
        # optionally provide an ID for a specific checkpoint,
        # otherwise the latest checkpoint is shown
        # "checkpoint_id": "1f029ca3-1f5b-6704-8004-820c16b69a5a"

    }
}
graph.get_state(config)

StateSnapshot(
    values={'messages': [HumanMessage(content="hi! I'm bob"), AIMessage(content='Hi Bob! How are you doing today?), HumanMessage(content="what's my name?"), AIMessage(content='Your name is Bob.')]}, next=(), 
    config={'configurable': {'thread_id': '1', 'checkpoint_ns': '', 'checkpoint_id': '1f029ca3-1f5b-6704-8004-820c16b69a5a'}},
    metadata={
        'source': 'loop',
        'writes': {'call_model': {'messages': AIMessage(content='Your name is Bob.')}},
        'step': 4,
        'parents': {},
        'thread_id': '1'
    },
    created_at='2025-05-05T16:01:24.680462+00:00',
    parent_config={'configurable': {'thread_id': '1', 'checkpoint_ns': '', 'checkpoint_id': '1f029ca3-1790-6b0a-8003-baf965b6a38f'}}, 
    tasks=(),
    interrupts=()
)

查看线程历史（检查点）¶

config = {
    "configurable": {
        "thread_id": "1"
    }
}
list(graph.get_state_history(config))

[
    StateSnapshot(
        values={'messages': [HumanMessage(content="hi! I'm bob"), AIMessage(content='Hi Bob! How are you doing today? Is there anything I can help you with?'), HumanMessage(content="what's my name?"), AIMessage(content='Your name is Bob.')]}, 
        next=(), 
        config={'configurable': {'thread_id': '1', 'checkpoint_ns': '', 'checkpoint_id': '1f029ca3-1f5b-6704-8004-820c16b69a5a'}}, 
        metadata={'source': 'loop', 'writes': {'call_model': {'messages': AIMessage(content='Your name is Bob.')}}, 'step': 4, 'parents': {}, 'thread_id': '1'},
        created_at='2025-05-05T16:01:24.680462+00:00',
        parent_config={'configurable': {'thread_id': '1', 'checkpoint_ns': '', 'checkpoint_id': '1f029ca3-1790-6b0a-8003-baf965b6a38f'}},
        tasks=(),
        interrupts=()
    ),
    StateSnapshot(
        values={'messages': [HumanMessage(content="hi! I'm bob"), AIMessage(content='Hi Bob! How are you doing today? Is there anything I can help you with?'), HumanMessage(content="what's my name?")]}, 
        next=('call_model',), 
        config={'configurable': {'thread_id': '1', 'checkpoint_ns': '', 'checkpoint_id': '1f029ca3-1790-6b0a-8003-baf965b6a38f'}},
        metadata={'source': 'loop', 'writes': None, 'step': 3, 'parents': {}, 'thread_id': '1'},
        created_at='2025-05-05T16:01:23.863421+00:00',
        parent_config={...}
        tasks=(PregelTask(id='8ab4155e-6b15-b885-9ce5-bed69a2c305c', name='call_model', path=('__pregel_pull', 'call_model'), error=None, interrupts=(), state=None, result={'messages': AIMessage(content='Your name is Bob.')}),),
        interrupts=()
    ),
    StateSnapshot(
        values={'messages': [HumanMessage(content="hi! I'm bob"), AIMessage(content='Hi Bob! How are you doing today? Is there anything I can help you with?')]}, 
        next=('__start__',), 
        config={...}, 
        metadata={'source': 'input', 'writes': {'__start__': {'messages': [{'role': 'user', 'content': "what's my name?"}]}}, 'step': 2, 'parents': {}, 'thread_id': '1'},
        created_at='2025-05-05T16:01:23.863173+00:00',
        parent_config={...}
        tasks=(PregelTask(id='24ba39d6-6db1-4c9b-f4c5-682aeaf38dcd', name='__start__', path=('__pregel_pull', '__start__'), error=None, interrupts=(), state=None, result={'messages': [{'role': 'user', 'content': "what's my name?"}]}),),
        interrupts=()
    ),
    StateSnapshot(
        values={'messages': [HumanMessage(content="hi! I'm bob"), AIMessage(content='Hi Bob! How are you doing today? Is there anything I can help you with?')]}, 
        next=(), 
        config={...}, 
        metadata={'source': 'loop', 'writes': {'call_model': {'messages': AIMessage(content='Hi Bob! How are you doing today? Is there anything I can help you with?')}}, 'step': 1, 'parents': {}, 'thread_id': '1'},
        created_at='2025-05-05T16:01:23.862295+00:00',
        parent_config={...}
        tasks=(),
        interrupts=()
    ),
    StateSnapshot(
        values={'messages': [HumanMessage(content="hi! I'm bob")]}, 
        next=('call_model',), 
        config={...}, 
        metadata={'source': 'loop', 'writes': None, 'step': 0, 'parents': {}, 'thread_id': '1'}, 
        created_at='2025-05-05T16:01:22.278960+00:00', 
        parent_config={...}
        tasks=(PregelTask(id='8cbd75e0-3720-b056-04f7-71ac805140a0', name='call_model', path=('__pregel_pull', 'call_model'), error=None, interrupts=(), state=None, result={'messages': AIMessage(content='Hi Bob! How are you doing today? Is there anything I can help you with?')}),), 
        interrupts=()
    ),
    StateSnapshot(
        values={'messages': []}, 
        next=('__start__',), 
        config={'configurable': {'thread_id': '1', 'checkpoint_ns': '', 'checkpoint_id': '1f029ca3-0870-6ce2-bfff-1f3f14c3e565'}},
        metadata={'source': 'input', 'writes': {'__start__': {'messages': [{'role': 'user', 'content': "hi! I'm bob"}]}}, 'step': -1, 'parents': {}, 'thread_id': '1'}, 
        created_at='2025-05-05T16:01:22.277497+00:00', 
        parent_config=None,
        tasks=(PregelTask(id='d458367b-8265-812c-18e2-33001d199ce6', name='__start__', path=('__pregel_pull', '__start__'), error=None, interrupts=(), state=None, result={'messages': [{'role': 'user', 'content': "hi! I'm bob"}]}),), 
        interrupts=()
    )
]

解耦返回值与保存值¶

使用 entrypoint.final 将返回给调用者的值与持久化到检查点的值解耦。这在以下情况下很有用：

您希望返回一个计算结果（例如，摘要或状态），但保存一个不同的内部值以供下次调用使用。
您需要控制在下一次运行中传递给上一个参数的内容。

^{API 参考：entrypoint | MemorySaver}

from typing import Optional
from langgraph.func import entrypoint
from langgraph.checkpoint.memory import MemorySaver

checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def accumulate(n: int, *, previous: Optional[int]) -> entrypoint.final[int, int]:
    previous = previous or 0
    total = previous + n
    # Return the *previous* value to the caller but save the *new* total to the checkpoint.
    return entrypoint.final(value=previous, save=total)

config = {"configurable": {"thread_id": "my-thread"}}

print(accumulate.invoke(1, config=config))  # 0
print(accumulate.invoke(2, config=config))  # 1
print(accumulate.invoke(3, config=config))  # 3

聊天机器人示例¶

一个使用函数式 API 和 MemorySaver 检查点的简单聊天机器人示例。该机器人能够记住之前的对话并从中断处继续。

^{API 参考：BaseMessage | add_messages | entrypoint | task | MemorySaver | ChatAnthropic}

from langchain_core.messages import BaseMessage
from langgraph.graph import add_messages
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import MemorySaver
from langchain_anthropic import ChatAnthropic

model = ChatAnthropic(model="claude-3-5-sonnet-latest")

@task
def call_model(messages: list[BaseMessage]):
    response = model.invoke(messages)
    return response

checkpointer = MemorySaver()

@entrypoint(checkpointer=checkpointer)
def workflow(inputs: list[BaseMessage], *, previous: list[BaseMessage]):
    if previous:
        inputs = add_messages(previous, inputs)

    response = call_model(inputs).result()
    return entrypoint.final(value=response, save=add_messages(inputs, response))

config = {"configurable": {"thread_id": "1"}}
input_message = {"role": "user", "content": "hi! I'm bob"}
for chunk in workflow.stream([input_message], config, stream_mode="values"):
    chunk.pretty_print()

input_message = {"role": "user", "content": "what's my name?"}
for chunk in workflow.stream([input_message], config, stream_mode="values"):
    chunk.pretty_print()

扩展示例：构建一个简单的聊天机器人

如何添加线程级持久化（函数式 API）：展示了如何向函数式 API 工作流添加线程级持久化并实现一个简单的聊天机器人。

长期记忆¶

长期记忆允许在不同的线程 ID 之间存储信息。这对于在一个对话中学习有关给定用户的信息并在另一个对话中使用它可能很有用。

扩展示例：添加长期记忆

如何添加跨线程持久化（函数式 API）：展示了如何向函数式 API 工作流添加跨线程持久化并实现一个简单的聊天机器人。

工作流¶

有关如何使用函数式 API 构建工作流的更多示例，请参阅工作流和代理指南。

代理¶

如何从零开始创建代理（函数式 API）：展示了如何使用函数式 API 从零开始创建一个简单代理。
如何构建多代理网络：展示了如何使用函数式 API 构建多代理网络。
如何在多代理应用程序中添加多轮对话（函数式 API）：允许最终用户与一个或多个代理进行多轮对话。

与其他库集成¶

使用函数式 API 将 LangGraph 功能添加到其他框架：将 LangGraph 的持久化、内存和流式传输等功能添加到其他不直接提供的代理框架中。