结构
虽然Pydantic / JSON解析器更加强大，但我们最初尝试的数据结构仅具有文本字段。
from langchain.output_parsers import StructuredOutputParser, ResponseSchema
from langchain.prompts import PromptTemplate, ChatPromptTemplate, HumanMessagePromptTemplate
from langchain.llms import OpenAI
from langchain.chat_models import ChatOpenAI
Here we define the response schema we want to receive.
response_schemas = [
ResponseSchema(name="answer", description="answer to the user's question"),
ResponseSchema(name="source", description="source used to answer the user's question, should be a website.")
]
output_parser = StructuredOutputParser.from_response_schemas(response_schemas)
We now get a string that contains instructions for how the response should be formatted, and we then insert that into our prompt.
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}
)
We can now use this to format a prompt to send to the language model, and then parse the returned result.
model = OpenAI(temperature=0)
_input = prompt.format_prompt(question="what's the capital of france")
output = model(_input.to_string())
output_parser.parse(output)
{'answer': 'Paris', 'source': 'https://en.wikipedia.org/wiki/Paris'}
And here’s an example of using this in a chat model
chat_model = ChatOpenAI(temperature=0)
prompt = ChatPromptTemplate(
messages=[
HumanMessagePromptTemplate.from_template("answer the users question as best as possible.\n{format_instructions}\n{question}")
],
input_variables=["question"],
partial_variables={"format_instructions": format_instructions}
)
_input = prompt.format_prompt(question="what's the capital of france")
output = chat_model(_input.to_messages())
output_parser.parse(output.content)
{'answer': 'Paris', 'source': 'https://en.wikipedia.org/wiki/Paris'}