LangChain/Pydantic_parser.py at main · ali3dev/LangChain · GitHub

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from llm import llm

from langchain.prompts import PromptTemplate
from langchain.prompts import ChatPromptTemplate

from langchain_google_genai import ChatGoogleGenerativeAI
from config import API_PROVIDER, GOOGLE_API_KEY, OPENAI_API_KEY
from langchain.output_parsers import ResponseSchema, StructuredOutputParser

from langchain.output_parsers import PydanticOutputParser
from pydantic import BaseModel, Field, field_validator
from typing import List

# Initialize Chat Model
chat = ChatGoogleGenerativeAI(model="gemini-1.5-flash", google_api_key=GOOGLE_API_KEY)


# Sample Email Response
email_response = """
Here's our itinerary for our upcoming trip to Europe.
There will be 5 of us on this vacation trip.
We leave from Denver, Colorado airport at 8:45 pm, and arrive in Amsterdam 10 hours later
at Schipol Airport.
We'll grab a ride to our airbnb and maybe stop somewhere for breakfast before
taking a nap.

Some sightseeing will follow for a couple of hours.
We will then go shop for gifts
to bring back to our children and friends.

The next morning, at 7:45am we'll drive to to Belgium, Brussels - it should only take aroud 3 hours.
While in Brussels we want to explore the city to its fullest - no rock left unturned!

"""

email_template = """
From the following email, extract the following information:

leave_time: when are they leaving for vacation to Europe. If there's an actual
time written, use it, if not write unknown.

leave_from: where are they leaving from, the airport or city name and state if
available.

cities_to_visit: extract the cities they are going to visit. If there are more than
one, put them in square brackets like '["cityone", "citytwo"].

Format the output as JSON with the following keys:
leave_time
leave_from
cities_to_visit

email: {email}
"""

# Define desired data structure
class VacationInfo(BaseModel):
    leave_time: str = Field(description="When they are leaving. It's usually")
    leave_from: str = Field(description="Where are they leaving from. It's a city, airport or state, or province")
    cities_to_visit: List[str] = Field(description="The cities, towns they will be visiting on their trip. This needs to be in a list")
    num_people: int = Field(description="This is an integer for a number of people on this trip")


    #  Updated validator for Pydantic v2
    @field_validator('num_people')
    @classmethod
    def check_num_people(cls, field):
        if field <= 0:
            raise ValueError("Badly formatted number")
        return field

# setup a parser and inect the instructions
pydantic_parser = PydanticOutputParser(pydantic_object=VacationInfo)
format_instructions = pydantic_parser.get_format_instructions()


# reviewed email template - we updated to add the {format_instructions}
email_template_revised = """
From the following email, extract the following information regarding
this trip.

email: {email}

{format_instructions}
"""


updated_prompt = ChatPromptTemplate.from_template(template=email_template_revised)
meassages = updated_prompt.format_messages(email=email_response,
                                           format_instructions=format_instructions)

format_response = chat(meassages)


vacation = pydantic_parser.parse(format_response.content)
print(type(vacation))
# print(vacation.cities_to_visit)
for item in vacation.cities_to_visit:
    print(f"Cities: {item}")