価格追跡ボットの構築
ECサイトの商品価格を監視し、値下げ時に通知を送信するボットを開発します。
「価格追跡ボットの構築」はCoddyKit上の無料Web Scraping & Botsレッスンです。 これはレッスン1/4です。 下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。 これはWeb Scraping & Bots学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Web Scraping & Botsコースには全4レッスンが含まれています。
このレッスンの一部はまだ翻訳されておらず、英語で表示されています。
What's a Price Tracker Bot?
Have you ever wanted to know when a product's price drops? A price tracker bot does exactly that!
It's an automated program that regularly checks the price of items on e-commerce websites.
When it detects a price change, especially a drop, it can notify you.
Bot's Core Tasks
Building a price tracker involves several key steps:
- Fetch: Get the product page content.
- Parse: Extract the price and product details.
- Store: Keep track of the last known price.
- Compare: Check if the current price is lower.
- Notify: Send an alert if a drop is found.
Spotting Product Details
Before we write code, we need to know where the information is on the page.
Using browser developer tools, you'd identify the HTML elements that contain the product's:
- Name
- Current Price
- Product URL
These are crucial for your bot to find the right data.
Getting the Web Page
The first step is to download the web page content. We'll use the requests library for this.
It sends an HTTP GET request to the product URL and retrieves the HTML.
Try running this simple example:
import requests
def fetch_page(url):
try:
response = requests.get(url)
response.raise_for_status() # Check for HTTP errors
return response.text
except requests.exceptions.RequestException as e:
print(f"Error fetching page: {e}")
return None
if __name__ == "__main__":
# Example URL (replace with a real product page for testing)
example_url = "https://example.com/product"
print(f"Fetching content from: {example_url}")
# In a real bot, you'd parse this content
# page_content = fetch_page(example_url)
# if page_content:
# print("Page content fetched successfully (first 200 chars):")
# print(page_content[:200])
# else:
# print("Failed to fetch page content.")
print("Page content fetching logic demonstrated.")Parsing the Price
Once you have the HTML, you'll use a library like BeautifulSoup to parse it and find the price.
Prices often come with currency symbols or extra text, so we'll need to clean the extracted string to get a numeric value.
Here's a snippet to illustrate:
from bs4 import BeautifulSoup
html_doc = """
<html><body>
<span class="product-price">$199.99</span>
<div id="item-name">Cool Gadget</div>
</body></html>
"""
soup = BeautifulSoup(html_doc, 'html.parser')
price_element = soup.find('span', class_='product-price')
if price_element:
price_string = price_element.get_text()
# Clean the string to get a float
cleaned_price = float(price_string.replace('$', '').strip())
print(f"Extracted Price: {cleaned_price}")
else:
print("Price element not found.")Remembering the Price
To track changes, your bot needs to remember the price it last saw. A simple way is to use a file to store this data.
For a basic bot, a JSON file or a simple dictionary in memory can work.
You'll store the product URL and its last known price.
import json
# Example of storing data
product_data = {
"https://example.com/product1": {
"name": "Cool Gadget",
"last_price": 199.99
},
"https://example.com/product2": {
"name": "Awesome Widget",
"last_price": 49.95
}
}
# In a real bot, you'd load/save this from a file
# with open('prices.json', 'w') as f:
# json.dump(product_data, f, indent=2)
print("Product data structure for storage:")
print(json.dumps(product_data, indent=2))Detecting Price Drops
This is the core logic! After fetching and parsing the new price, you compare it with the stored "last price".
If the new price is lower than the stored price, you've found a deal!
You should also update the stored price with the new one for future comparisons.
current_price = 189.99
stored_price = 199.99
product_name = "Cool Gadget"
if current_price < stored_price:
print(f"PRICE DROP ALERT! {product_name} is now ${current_price} (was ${stored_price})")
# Update stored_price = current_price in your data
elif current_price > stored_price:
print(f"Price increased for {product_name}. Current: ${current_price}, Was: ${stored_price}")
# Update stored_price = current_price
else:
print(f"Price for {product_name} remains ${current_price}")Notifying About Deals
Once a price drop is detected, your bot needs to tell you!
For a simple bot, printing a message to the console is enough. For real-world use, you might:
- Send an email
- Push a notification to your phone
- Send a message to a chat app (e.g., Discord, Telegram)
def send_notification(product_name, old_price, new_price):
message = (
f"🚨 Price Drop Alert! 🚨\n"
f"Product: {product_name}\n"
f"Old Price: ${old_price:.2f}\n"
f"New Price: ${new_price:.2f}\n"
f"Check it out now!"
)
print(message)
# In a real app, you'd integrate email/SMS here
if __name__ == "__main__":
send_notification("Awesome Headphones", 250.00, 225.00)Your First Price Tracker
Let's combine these pieces into a basic, runnable price tracker. This example simulates fetching and parsing.
Remember, for a real bot, you'd replace the `mock_fetch_and_parse` with actual requests and BeautifulSoup calls.
import json
import random
# Mock functions for demonstration
def mock_fetch_and_parse(product_url):
# Simulate different prices
if "gadget" in product_url:
return random.choice([199.99, 189.99, 205.00])
return random.choice([49.95, 45.00, 52.00])
def send_notification(product_name, old_price, new_price):
print(f"🚨 Price Drop! {product_name} is now ${new_price:.2f} (was ${old_price:.2f})")
# Main logic
def check_price(product_url, product_name, stored_prices):
current_price = mock_fetch_and_parse(product_url)
last_price = stored_prices.get(product_url)
if last_price is None:
print(f"First check for {product_name}: ${current_price:.2f}")
elif current_price < last_price:
send_notification(product_name, last_price, current_price)
elif current_price > last_price:
print(f"Price for {product_name} increased to ${current_price:.2f}")
else:
print(f"Price for {product_name} remains ${current_price:.2f}")
stored_prices[product_url] = current_price # Update price
if __name__ == "__main__":
# Simulate stored prices (from a file in a real app)
my_tracked_items = {
"https://example.com/gadget": 200.00, # Initial price
"https://example.com/widget": 50.00
}
print("--- First Run ---")
check_price("https://example.com/gadget", "Cool Gadget", my_tracked_items)
check_price("https://example.com/widget", "Awesome Widget", my_tracked_items)
print("\n--- Second Run ---")
check_price("https://example.com/gadget", "Cool Gadget", my_tracked_items)
check_price("https://example.com/widget", "Awesome Widget", my_tracked_items)
print("\nFinal tracked prices:", json.dumps(my_tracked_items, indent=2))Price Logic Check
Consider a price tracker bot. It last recorded a product price of $50.00. On its next run, it fetches the price as $45.00. What should the bot do?
Recap & Next Steps
You've learned the fundamental steps to build a price tracker bot!
- Fetch HTML with
requests. - Parse prices with
BeautifulSoup. - Store prices (e.g., in a JSON file).
- Compare current vs. stored prices.
- Notify on price drops.
Next steps include scheduling your bot to run automatically and exploring more advanced notification methods.
よくある質問
「価格追跡ボットの構築」レッスンは無料ですか？
はい。「価格追跡ボットの構築」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Web Scraping & Botsコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Web Scraping & Botsコースには全4レッスンが含まれています。
「価格追跡ボットの構築」で何を学びますか？
ECサイトの商品価格を監視し、値下げ時に通知を送信するボットを開発します。 ブラウザで直接実行するハンズオンコードでWeb Scraping & Botsを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。
Web Scraping & Botsを始めるのに経験は必要ですか？
事前経験は必要ありません。CoddyKitのWeb Scraping & Botsは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。 これはレッスン1/4です。
「価格追跡ボットの構築」レッスンにはどのくらい時間がかかりますか？
ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。
このWeb Scraping & Botsレッスンでコードを書いて実行できますか？
はい。すべてのWeb Scraping & Botsレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。