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.