Python新手求助：如何创建可检测特定按钮内链接变化的网站更新工具

Hey there! Since you're new to Python and trying to build a tool to monitor a specific button's link on that Kelda Group page, let's break this down into easy, actionable steps.

Your current code grabs every <a> tag on the page, which is why you're seeing so many links. Since your target link is in a fixed position, we can use HTML element attributes (like class, ID, or surrounding parent elements) to pinpoint it directly.

How to find the right attributes: #

Right-click the target button on the webpage → select "Inspect" to view its HTML structure. Look for unique identifiers like:

• A specific class (e.g., btn-creditor-document)
• A unique id (e.g., latest-creditor-link)
• Exact button text (e.g., "Download Creditor Report")
• A parent container with a distinct class/id (e.g., a <div> wrapping the button)

Example code for precise targeting: #

import requests
from bs4 import BeautifulSoup

url = 'https://www.keldagroup.com/investors/creditor-considerations/'
reqs = requests.get(url)
soup = BeautifulSoup(reqs.text, 'html.parser')

# Option 1: Target by button class (replace with your button's actual class)
target_link = soup.find('a', class_='btn-creditor-document')

# Option 2: Target by button text (match the exact text on the button)
# target_link = soup.find('a', string='Download Creditor Report')

# Option 3: Target via parent container (e.g., a div with class "creditor-section")
# target_link = soup.select_one('div.creditor-section a:first-of-type')

# Extract and print the link if found
if target_link:
    href = target_link.get('href')
    print(f"Target link found: {href}")
else:
    print("Could not locate the target link—double-check your selector!")

Once you can reliably fetch the target link, you can compare it to a saved version to check for updates. Here's a simple implementation:

import requests
from bs4 import BeautifulSoup

def get_target_link():
    url = 'https://www.keldagroup.com/investors/creditor-considerations/'
    reqs = requests.get(url)
    soup = BeautifulSoup(reqs.text, 'html.parser')
    # Use your confirmed selector here
    target_link = soup.select_one('div.creditor-section a.btn')
    return target_link.get('href') if target_link else None

def check_link_update():
    # Read the last saved link (if exists)
    try:
        with open('saved_link.txt', 'r') as f:
            old_link = f.read().strip()
    except FileNotFoundError:
        old_link = None

    new_link = get_target_link()

    if not new_link:
        print("Error: Failed to fetch target link.")
        return

    if not old_link:
        print("First run—saving initial link.")
        with open('saved_link.txt', 'w') as f:
            f.write(new_link)
    elif new_link != old_link:
        print(f"Link updated! Old: {old_link}\nNew: {new_link}")
        # Add notifications here (e.g., email, desktop alert) if needed
        with open('saved_link.txt', 'w') as f:
            f.write(new_link)
    else:
        print("No changes detected.")

if __name__ == "__main__":
    check_link_update()

For a more robust setup with less manual code, consider these tools:

• requests-cache: Caches webpage requests to avoid redundant downloads (saves bandwidth and speeds up checks). Install with pip install requests-cache.
• schedule: Automates periodic checks (e.g., run daily at 9 AM). Install with pip install schedule.

Example with both tools: #

import requests
from bs4 import BeautifulSoup
import requests_cache
import schedule
import time

# Cache requests for 1 hour to avoid hitting the site too often
requests_cache.install_cache('kelda_cache', expire_after=3600)

def get_target_link():
    url = 'https://www.keldagroup.com/investors/creditor-considerations/'
    reqs = requests.get(url)
    soup = BeautifulSoup(reqs.text, 'html.parser')
    return soup.select_one('div.creditor-section a.btn').get('href')

def check_link_update():
    try:
        with open('saved_link.txt', 'r') as f:
            old_link = f.read().strip()
    except FileNotFoundError:
        old_link = None

    new_link = get_target_link()
    if new_link != old_link:
        print(f"Link updated! Old: {old_link}\nNew: {new_link}")
        with open('saved_link.txt', 'w') as f:
            f.write(new_link)
    else:
        print("No changes.")

# Schedule daily checks at 9 AM
schedule.every().day.at("09:00").do(check_link_update)

print("Monitoring link changes... Press Ctrl+C to stop.")
while True:
    schedule.run_pending()
    time.sleep(60)

内容的提问来源于stack exchange，提问作者van10