主题
Functional API 允许您以最小的代码改动,为您的应用程序添加 LangGraph 的核心功能——持久化、记忆、人在回路 和 流式传输。
有关 Functional API 的概念性信息,请参阅 Functional API。
创建简单工作流
定义 entrypoint 时,输入被限制为函数的第一个参数。要传递多个输入,可以使用字典。
python
@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
python
import uuid
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import InMemorySaver
# 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 = InMemorySaver()
@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:使用 LLM 撰写文章
此示例演示了如何在语法上使用 @task 和 @entrypoint 装饰器。如果提供了检查点存储器,工作流结果将被持久化在其中。
python
import uuid
from langchain.chat_models import init_chat_model
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import InMemorySaver
model = init_chat_model('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 model.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 = InMemorySaver()
@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
可以通过并发调用任务并等待结果来实现并行执行。这对于提高 I/O 密集型任务的性能(例如,调用 LLM 的 API)非常有用。
python
@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,结果被合并成一个单一的文本输出。
python
import uuid
from langchain.chat_models import init_chat_model
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import InMemorySaver
# Initialize the LLM model
model = init_chat_model("gpt-3.5-turbo")
# Task that generates a paragraph about a given topic
@task
def generate_paragraph(topic: str) -> str:
response = model.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 = InMemorySaver()
@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)此示例利用 LangGraph 的并发模型来改善执行时间,特别是在任务涉及 I/O(如 LLM 补全)时。
调用图
Functional API 和 Graph 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。
python
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 Functional API 调用简单图
python
import uuid
from typing import TypedDict
from langgraph.func import entrypoint
from langgraph.checkpoint.memory import InMemorySaver
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 = InMemorySaver()
@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 task 内部调用其他 entrypoint。
python
@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
python
import uuid
from langgraph.func import entrypoint
from langgraph.checkpoint.memory import InMemorySaver
# Initialize a checkpointer
checkpointer = InMemorySaver()
# 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
Functional API 使用与 Graph API 相同的流式传输机制。请阅读 流式传输指南 部分以获取更多详细信息。
使用流式 API 同时流式传输更新和自定义数据的示例。
python
from langgraph.func import entrypoint
from langgraph.checkpoint.memory import InMemorySaver
from langgraph.config import get_stream_writer
checkpointer = InMemorySaver()
@entrypoint(checkpointer=checkpointer)
def main(inputs: dict) -> int:
writer = get_stream_writer()
writer("Started processing")
result = inputs["x"] * 2
writer(f"Result is {result}")
return result
config = {"configurable": {"thread_id": "abc"}}
for mode, chunk in main.stream(
{"x": 5},
stream_mode=["custom", "updates"],
config=config
):
print(f"{mode}: {chunk}")- 从
langgraph.config导入get_stream_writer。 - 在入口点内获取一个流写入器实例。
- 在计算开始前发出自定义数据。
- 计算完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。
pycon
('updates', {'add_one': 2})
('updates', {'add_two': 3})
('custom', 'hello')
('custom', 'world')
('updates', {'main': 5})Python < 3.11 下的异步 如果使用 Python < 3.11 并编写异步代码,使用 get_stream_writer 将无效。请直接使用 StreamWriter 类。更多详情请参阅 Python < 3.11 下的异步。
python
from langgraph.types import StreamWriter
@entrypoint(checkpointer=checkpointer)
async def main(inputs: dict, writer: StreamWriter) -> int:
...重试策略
python
from langgraph.checkpoint.memory import InMemorySaver
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 = InMemorySaver()
@entrypoint(checkpointer=checkpointer)
def main(inputs, writer):
return get_info().result()
config = {
"configurable": {
"thread_id": "1"
}
}
main.invoke({'any_input': 'foobar'}, config=config)pycon
'OK'缓存任务
python
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))
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。缓存将在此时间后失效。
错误后恢复执行
python
import time
from langgraph.checkpoint.memory import InMemorySaver
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 = InMemorySaver()
@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,不需要重新运行 slow_task,因为其结果已保存在检查点中。
python
main.invoke(None, config=config)pycon
'Ran slow task.'人在回路
Functional API 支持使用 interrupt 函数和 Command 原语实现 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"。 - 暂停等待人工输入。恢复时,追加人工输入。
- 追加
"qux"。
python
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"现在,我们可以在一个 入口点 中组合这些任务:
python
from langgraph.checkpoint.memory import InMemorySaver
checkpointer = InMemorySaver()
@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_3interrupt() 在任务内部被调用,使人工能够审查和编辑前一个任务的输出。先前任务(本例中为 step_1)的结果会被持久化,因此在 interrupt 之后不会再次运行。
让我们发送一个查询字符串:
python
config = {"configurable": {"thread_id": "1"}}
for event in graph.stream("foo", config):
print(event)
print("\n")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 任务期望数据的 Command。
python
# Continue execution
for event in graph.stream(Command(resume="baz"), config):
print(event)
print("\n")恢复后,运行继续执行剩余步骤并按预期终止。
审查工具调用
要在执行前审查工具调用,我们添加一个调用 interrupt 的 review_tool_call 函数。当调用此函数时,执行将暂停,直到我们发出恢复命令。
给定一个工具调用,我们的函数将 interrupt 以等待人工审查。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)
python
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"]
)现在我们可以更新我们的 入口点 来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(本例中是初始模型调用)的结果会被持久化,因此在 interrupt 之后不会再次运行。
python
from langgraph.checkpoint.memory import InMemorySaver
from langgraph.graph.message import add_messages
from langgraph.types import Command, interrupt
checkpointer = InMemorySaver()
@entrypoint(checkpointer=checkpointer)
def agent(messages, previous):
if previous is not None:
messages = add_messages(previous, messages)
model_response = call_model(messages).result()
while True:
if not model_response.tool_calls:
break
# Review tool calls
tool_results = []
tool_calls = []
for i, tool_call in enumerate(model_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:
model_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,
[model_response, *tool_results, *remaining_tool_results],
)
# Call model again
model_response = call_model(messages).result()
# Generate final response
messages = add_messages(messages, model_response)
return entrypoint.final(value=model_response, save=messages)短期记忆
短期记忆允许跨同一 线程 ID 的不同 调用 存储信息。更多详情请参阅 短期记忆。
管理检查点
您可以查看和删除检查点存储器存储的信息。
查看线程状态
python
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=()
)查看线程的历史记录
python
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=()
)
]分离返回值与保存值
使用 entrypoint.final 可以将返回给调用者的内容与保存在检查点中的内容分离开来。这在以下情况下很有用:
- 您想返回一个计算结果(例如,摘要或状态),但保存一个不同的内部值供下次调用使用。
- 您需要控制下一次运行时传递给前一个参数的内容。
python
from langgraph.func import entrypoint
from langgraph.checkpoint.memory import InMemorySaver
checkpointer = InMemorySaver()
@entrypoint(checkpointer=checkpointer)
def accumulate(n: int, *, previous: int | None) -> 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 Functional API 和 InMemorySaver 检查点存储器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上次中断的地方继续。
python
from langchain.messages import BaseMessage
from langgraph.graph import add_messages
from langgraph.func import entrypoint, task
from langgraph.checkpoint.memory import InMemorySaver
from langchain_anthropic import ChatAnthropic
model = ChatAnthropic(model="claude-sonnet-4-5-20250929")
@task
def call_model(messages: list[BaseMessage]):
response = model.invoke(messages)
return response
checkpointer = InMemorySaver()
@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()长期记忆
长期记忆 允许跨不同的 线程 ID 存储信息。这对于在一次对话中学习关于特定用户的信息并在另一次对话中使用它可能很有用。
工作流
- 工作流和智能体 指南,获取更多关于如何使用 Functional API 构建工作流的示例。
与其他库集成
- 使用 Functional API 将 LangGraph 的功能添加到其他框架:将 LangGraph 的功能(如持久化、记忆和流式传输)添加到其他默认不提供这些功能的智能体框架中。