Project 4: Photo Caption Bot
AI Engineer
Builds on these lessons
Current Task
Objective
An LLMChain bundles a PromptTemplate and a model into a single reusable object with one .invoke() call.
Task: build a prompt, wire it into a chain with a model, and print the chain's input keys.
index.py
from langchain_core.prompts import PromptTemplate
from langchain_openai import ChatOpenAI
prompt = PromptTemplate(
template="Caption this photo: {description}",
input_variables=["description"],
)
model = ChatOpenAI(model="gpt-4o-mini")
chain = prompt | model
print(chain.input_schema.model_json_schema()["required"])
* Hint: Correct characters turn green, incorrect ones turn red.
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