PromptTemplate basics in LangChain - Mini Project: Build & Apply

PromptTemplate basics

📖 Scenario: You are building a simple chatbot that uses a prompt template to ask questions. The prompt template will help you create messages with placeholders for user input.

🎯 Goal: Create a PromptTemplate that takes a user's name and question, then formats a message asking the question politely.

📋 What You'll Learn

Create a PromptTemplate with input variables name and question.

Set the template string to: 'Hello {name}, can you please answer: {question}?'

Use the format method to fill in the template with example values.

Print the formatted prompt message.

💡 Why This Matters

🌍 Real World

PromptTemplate helps create dynamic messages for chatbots, AI assistants, or any system that needs to ask questions or generate text with user input.

💼 Career

Understanding PromptTemplate is useful for AI developers, chatbot builders, and anyone working with language models to create flexible and reusable prompts.

1

Import PromptTemplate and create the template

Import PromptTemplate from langchain.prompts and create a variable called template that is a PromptTemplate with input variables name and question, and the template string set to 'Hello {name}, can you please answer: {question}?' .

LangChain

# Import PromptTemplate and create the template
# Your code here

Need a hint?

Use PromptTemplate(input_variables=[...], template=...) to create the template.

2

Create example input values

Create a dictionary called inputs with keys 'name' and 'question'. Set 'name' to 'Alice' and 'question' to 'What is the weather today'.

LangChain

from langchain.prompts import PromptTemplate

template = PromptTemplate(input_variables=["name", "question"], template="Hello {name}, can you please answer: {question}?")

# Create the inputs dictionary
# Your code here

Need a hint?

Use a dictionary with exact keys and values as shown.

3

Format the prompt with inputs

Use the format method of template with the inputs dictionary to create a variable called formatted_prompt.

LangChain

from langchain.prompts import PromptTemplate

template = PromptTemplate(input_variables=["name", "question"], template="Hello {name}, can you please answer: {question}?")

inputs = {"name": "Alice", "question": "What is the weather today"}

# Format the prompt using the inputs
# Your code here

Need a hint?

Use template.format(**inputs) to fill the template.

4

Print the formatted prompt

Write a line to print the variable formatted_prompt.

LangChain

from langchain.prompts import PromptTemplate

template = PromptTemplate(input_variables=["name", "question"], template="Hello {name}, can you please answer: {question}?")

inputs = {"name": "Alice", "question": "What is the weather today"}

formatted_prompt = template.format(**inputs)

# Print the formatted prompt
# Your code here

Need a hint?

Use print(formatted_prompt) to show the final message.