langchain实现大模型结构化输出

前言

这里大模型使用GLM4。
结构化输出的稳定性与大模型的能力挂钩
听话的就容易出
不听话的就容易报错
langchain实现大模型结构化输出，实际上就帮助我们构建一套提示词
对模型的约束也是十分有限的
但是仍然可以用

大模型对话函数

import requests
import json
from typing import *from openai import OpenAIbase_url = "http://127.0.0.1:8023/v1/"
client = OpenAI(api_key="EMPTY", base_url=base_url)def simple_chat(use_stream=False, query=None):messages = []messages.append({"role": "user","content": query})response = client.chat.completions.create(model="glm-4",messages=messages,stream=use_stream,max_tokens=256,temperature=0.4,presence_penalty=1.2,top_p=0.8,)# 检查响应是否存在并且有 'choices' 键if response and hasattr(response, 'choices'):# 打印出所有的选择（回答）for choice in response.choices:# 检查 'message' 键是否存在于选择中if hasattr(choice, 'message'):# 打印回答的内容print(choice.message.content)   return choice.message.contentelse:print("Error:", response.status_code if response else "No response received.")

首先GLM4使用openai的方式启动，然后配置好端口号就行了。
输入一句回答一句
代码参考GLM4官方的代码修改而来。

返回列表格式

# 返回列表格式
from langchain_core.output_parsers.list import CommaSeparatedListOutputParser
from langchain_core.prompts import PromptTemplateoutput_parser = CommaSeparatedListOutputParser()format_instructions = output_parser.get_format_instructions()
prompt = PromptTemplate(template="列出几种{subject}.\n{format_instructions}",input_variables=["subject"],partial_variables={"format_instructions": format_instructions + "用中文回答"}
)
prompt = prompt.format(subject="水果")print("prompt"+"*"*10)
print(prompt)
print("prompt"+"*"*10)
prompt = str(prompt)
output = simple_chat(query=prompt)
print("output"+"*"*10)
print(output)
print("output_parser"+"*"*10)
print(output_parser.parse(output))
print("output_parser"+"*"*10)

output_parser就是一个结构化输出的提示词模板
prompt就是使用langchain模板构建的提示词
提示词输入大模型即可生成结果
结果由output_parser解析，就能得到我们需要的结构化输出结果
上述代码运行结果为：

也就是说langchain的工具帮助我们进行结构化输出，就是帮助我们构建结构化提示词和对结果进行结构化解析。

所以说，这里最重要的就是提示词的构建。

下面的讲述都只放出提示词，因为大模型喂入那部分都是相同的。

返回对象类型

from typing import Optionalfrom langchain_core.pydantic_v1 import BaseModel, Field
from langchain_core.output_parsers.pydantic import PydanticOutputParser
from langchain_core.prompts import PromptTemplateclass Student(BaseModel):name: str = Field(description="学生的姓名")age: str = Field(description="学生的年龄")student_query = "告诉我一个学生的信息"output_parser = PydanticOutputParser(pydantic_object=Student)prompt = PromptTemplate(template="回答下面问题.\n{format_instructions}\n{query}\n",input_variables=["query"],partial_variables={"format_instructions": output_parser.get_format_instructions()+"用中文回答"},
)prompt = prompt.format_prompt(query=student_query)

返回对象格式（信息抽取）

from typing import Optionalfrom langchain_core.pydantic_v1 import BaseModel, Field
from langchain_core.output_parsers.pydantic import PydanticOutputParser
from langchain_core.prompts import PromptTemplateclass Person(BaseModel):name: Optional[str] = Field(default=None, description="The name of the person")hair_color: Optional[str] = Field(default=None, description="The color of the peron's hair if known")height_in_meters: Optional[str] = Field(default=None, description="Height measured in meters")
text = "Alan Smith is 1.65m tall.\n"
query = textoutput_parser = PydanticOutputParser(pydantic_object=Person)prompt = PromptTemplate(template='''system:\nYou are an expert extraction algorithm.\nOnly extract relevant information from the text.\nIf you do not know the value of an attribute asked to extract\nreturn null for the attribute's value.\n{format_instructions}\nhuman:{query}\n''',input_variables=["query"],partial_variables={"format_instructions": output_parser.get_format_instructions()},
)prompt = prompt.format_prompt(query=query)

返回json格式

# 返回json格式
# case1
from langchain.output_parsers import ResponseSchema, StructuredOutputParser
from langchain_core.prompts import PromptTemplate
response_schemas = [ResponseSchema(name="name", description="学生的姓名"),ResponseSchema(name="age", description="学生的年龄")
]
output_parser = StructuredOutputParser.from_response_schemas(response_schemas)format_instructions = output_parser.get_format_instructions()
prompt = PromptTemplate(template="回答下面问题.\n{format_instructions}\n{question}",input_variables=["question"],partial_variables={"format_instructions": format_instructions}
)
prompt = prompt.format_prompt(question="给我一个女孩的信息")# case2
from langchain.output_parsers import ResponseSchema, StructuredOutputParser
from langchain_core.prompts import PromptTemplate
response_schemas = [ResponseSchema(name="answer", description="地名"),ResponseSchema(name="source",description="答案的网址",),
]
output_parser = StructuredOutputParser.from_response_schemas(response_schemas)format_instructions = output_parser.get_format_instructions()
prompt = PromptTemplate(template="answer the users question as best as possible.\n{format_instructions}\n{question}",input_variables=["question"],partial_variables={"format_instructions": format_instructions},
)
prompt = prompt.format_prompt(question="华为公司的总部在哪里？")# 据说弱点的模型用上面的方式来返回json效果会好点
# case3
from langchain_core.output_parsers import JsonOutputParser
from langchain_core.prompts import PromptTemplate
from langchain_core.pydantic_v1 import BaseModel, Field# Define your desired data structure.
class Joke(BaseModel):setup: str = Field(description="question to set up a joke")punchline: str = Field(description="answer to resolve the joke")# And a query intented to prompt a language model to populate the data structure.
query = "讲一个笑话"# Set up a parser + inject instructions into the prompt template.
output_parser = JsonOutputParser(pydantic_object=Joke)prompt = PromptTemplate(template="Answer the user query.\n{format_instructions}\n{query}\n",input_variables=["query"],partial_variables={"format_instructions": output_parser.get_format_instructions()},
)
prompt = prompt.format_prompt(query=query)

做选择题（在给定答案中选一个答案）

from langchain.output_parsers.enum import EnumOutputParserfrom enum import Enumclass Colors(Enum):RED = "red"GREEN = "green"BLUE = "blue"BLACK = "black"OTHER = "other"output_parser = EnumOutputParser(enum=Colors)from langchain_core.prompts import PromptTemplate
from langchain_openai import ChatOpenAIprompt = PromptTemplate.from_template("""这个人的眼睛可能是什么颜色的?你只需要说出答案就行了> Person: {person}Instructions: {instructions}"""
).partial(instructions=output_parser.get_format_instructions())
prompt = prompt.format_prompt(person="在中国的小明有一双水汪汪的眼睛")