Building a Price Tracker Bot

Architecture

1. Fetch product page (or API)
2. Parse price
3. Save price history (CSV/SQLite)
4. Compare with threshold
5. Notify (email/telegram)

Example: parse a price from HTML

price_parse_template.py

from bs4 import BeautifulSoup
 
html = "<span class='price'>$199.99</span>"
soup = BeautifulSoup(html, "html.parser")
price_text = soup.select_one(".price").get_text(strip=True)
print(price_text)

Persist history (CSV)

save_history.py

import csv
from datetime import datetime
 
 
def append_price(csv_path: str, price: str):
    with open(csv_path, "a", newline="", encoding="utf-8") as f:
        w = csv.writer(f)
        w.writerow([datetime.now().isoformat(), price])

Notes

Real sites often block scraping.

Prefer APIs, and respect site policies.

Visualize it

A tracker bot loops through fetch, parse, and store steps, retrying politely when a request fails.

diagram Price tracker loop mermaid

  flowchart TD
    A["Fetch the page"] --> B{"Request successful?"}
    B -- "No" --> E["Wait/retry (respect rate limits)"]
    E --> A
    B -- "Yes" --> C["Parse the HTML"]
    C --> D["Extract the price"]
    D --> F["Store it"]

How the bot fetches, parses, and stores prices, with retry on failure