Cost tracking across runs in LangChain - Mini Project: Build & Apply

Cost Tracking Across Runs with Langchain

📖 Scenario: You are building a simple Langchain application that calls an AI model multiple times. You want to keep track of the total cost spent on these calls across different runs of your program.This helps you understand how much you are spending and manage your budget better.

🎯 Goal: Create a Langchain program that tracks the total cost of AI calls across multiple runs by saving and loading the cost from a file.You will set up the initial cost data, configure the file path, update the cost after each call, and save the total cost back to the file.

📋 What You'll Learn

Create a variable to hold the total cost loaded from a file

Create a variable for the file path to store the cost

Update the total cost after a simulated AI call

Save the updated total cost back to the file

💡 Why This Matters

🌍 Real World

Tracking costs helps developers manage their spending on AI services and avoid surprises in billing.

💼 Career

Many jobs require monitoring API usage costs, especially when working with cloud AI services like Langchain.

1

Set up initial total cost variable

Create a variable called total_cost and set it to 0.0 to represent the starting cost before any AI calls.

LangChain

# Your code here

Need a hint?

Think of total_cost as your wallet balance starting at zero.

2

Add file path configuration for cost storage

Create a variable called cost_file_path and set it to the string 'cost_data.txt' to store the total cost between runs.

LangChain

total_cost = 0.0
# Your code here

Need a hint?

This file will act like a notebook where you write down your spending.

3

Update total cost after an AI call

Add code to simulate an AI call cost of 0.05 and add it to total_cost. Use ai_call_cost = 0.05 and then update total_cost by adding ai_call_cost.

LangChain

total_cost = 0.0
cost_file_path = 'cost_data.txt'
# Your code here

Need a hint?

Think of ai_call_cost as the price of one coffee you just bought, adding to your total spending.

4

Save the updated total cost to the file

Add code to open the file at cost_file_path in write mode and save the string version of total_cost to it. Use with open(cost_file_path, 'w') as f: and f.write(str(total_cost)).

LangChain

total_cost = 0.0
cost_file_path = 'cost_data.txt'
ai_call_cost = 0.05
total_cost += ai_call_cost
# Your code here

Need a hint?

Saving your spending in a file is like writing it down in your diary.