Category: devops

Building a Telegram Expense Tracker Bot with Google Sheets and Docker

I recently built a personal finance tool that lets me log expenses via Telegram, automatically categorizes them, and records everything in Google Sheets.

The goal? Make budgeting fast, private, and mobile-friendly — even from a Raspberry Pi.

This post explains how to reproduce it, what I learned, and where it got interesting.

What I Built

A Telegram bot that lets me send messages like:

groceries 12.50
uber 8.90
coffee -4.00

The bot:

  • Parses the text and categorizes the expense
  • Applies budget tracking with alerts if I’m close to my monthly limit
  • Logs the expense into a Google Sheet using a service account
  • Runs on a Raspberry Pi using Docker

Technologies Used

  • Python + python-telegram-bot (v20)
  • Google Sheets API via service accounts
  • Docker (with ARM build for Raspberry Pi)
  • Poetry for Python dependency management
  • YAML configs for budgets, users, and categories
  • Makefile for workflow automation

How to Reproduce It

  • Create a Telegram bot with @BotFather
  • Generate a Google service account and share a Sheet with it
  • Configure your categories and budget limits in budgets.yaml
  • Whitelist Telegram user IDs in users.yaml
  • Mount the secrets into Docker using bind volumes
  • Run it on a Raspberry Pi (with a lightweight ARM-compatible image)

Interesting Challenges

Dynamic Configuration Reloading

I wanted to update users.yaml without restarting the bot. To do that:

  • I implemented an in-memory cache with a TTL
  • It reloads configs every few seconds if the file changes
  • Updates deployable via make deploy-users over SSH

Smart Expense Parsing

  • Messages like "food -3.50" are parsed with regex
  • I used word-boundary matching to avoid false positives (e.g., “car” in “carbonara”)
  • Negative values allow for reimbursements

Secret Management in Docker

  • Rather than baking credentials into the image, I mounted them at runtime
  • Paths are resolved dynamically based on the users.yaml file location
  • This made it secure and flexible across environments

Custom Budgets Per User

  • Each user can define their own monthly budgets per category
  • If none is defined, the app falls back to the shared config
  • Budget overages trigger alerts at 25%, 50%, and 75%

Local vs. Docker Consistency

I ensured:

  • All paths in users.yaml are relative and resolved based on file location
  • The same users.yaml works in local dev and in Docker on the Pi
  • Deployment is as easy as: make build-arm && make deploy && make run-on-pi

Ideas for the Future

  • Zero-shot category classification using AI instead of static keywords
  • Multi-user dashboards with shared budgets
  • Voice input or receipt photo parsing

TL;DR

I built a Telegram bot that logs categorized expenses into Google Sheets, tracks budgets, and runs on a Raspberry Pi — using clean Python, YAML configs, and Docker. It was a great blend of DevOps, API integration, and practical problem-solving.