📧 Automated Invoice Reminder

👋 About The Project

I built this automation tool to solve a specific problem: manually checking Excel sheets for unpaid invoices and writing email reminders is tedious and prone to error.

This Python script automates the entire process. It reads a local dataset (data.csv), checks who is late on their payment, and uses the Gmail API to send them a personalized, professional HTML email instantly.

It was a great project for me to learn how to connect Python scripts to real-world APIs and handle data securely.

⚙️ How It Works

• Smart Date Checking: The script runs through my client list using Pandas. It compares today's date with the reminder_date column to decide exactly who needs an email.
• No Hardcoded Passwords: Instead of putting my Gmail password in the code (which is unsafe), I implemented OAuth 2.0. The script logs in once via a browser window, saves a secure token, and uses that for future runs.
• Custom HTML Emails: I didn't want to send plain text. The script injects the client's name, invoice number, and amount into an HTML template so the emails look professional.

🛠️ Tech Stack

• Python 3.10+

• Pandas (for reading CSVs and handling dates)

• Gmail API & Google Client Library (for sending the emails)

• OAuth 2.0 (for secure authentication)

• Security Note You won't find my client_secret.json or data.csv files here. I excluded them using .gitignore to keep my API keys and personal data safe. You will need to provide your own to test the code!