如何用Python抓取mbasic.facebook.com指定class的a标签

Hey there! Let's break down why your regex attempts aren't working and walk through a couple of reliable solutions to grab those <a class="cf"> tags you need.

What's Wrong With Your Regex Code? #

First, let's look at the issues in your existing attempts:

1. First Regex Attempt:

   • You used re.compile(driver.page_source) which is backwards—re.compile() takes a regex pattern, not the page source.
   • The pattern "<a class=\"cf\" href=\"*\">" uses * incorrectly. In regex, * is a quantifier (matches 0+ of the previous character), not a wildcard. You'd need .*? to match any characters inside the href, but even then, HTML tags often have extra attributes (like target) or whitespace that would break this rigid pattern.

2. Second Regex Attempt:

   • Your pattern is targeting <td> elements containing an <a> with any class, not specifically the cf class. It's also too broad and will fail if the HTML has line breaks or unexpected spacing between attributes.

Regex is rarely a good choice for parsing HTML—HTML is structured, and dedicated parsers handle things like whitespace, attribute order, and nested elements way better.

Solution 1: Use Selenium's Built-in Locators (Simplest) #

Since you're already using Selenium, you can directly locate the elements you need without regex. Selenium has built-in methods to find elements by CSS selectors, which are perfect for this:

from selenium import webdriver
from selenium.webdriver.common.by import By

# Initialize your driver (adjust for your browser, e.g., Firefox, Edge)
driver = webdriver.Chrome()

# Navigate to the target page
driver.get('https://mbasic.facebook.com/cheska.cabral.796/friends')

# Find all <a> tags with class "cf" using CSS selector
target_links = driver.find_elements(By.CSS_SELECTOR, "a.cf")

# Print each full <a> tag HTML
for link in target_links:
    print(link.get_attribute('outerHTML'))

# Clean up
driver.quit()

Solution 2: Use BeautifulSoup for HTML Parsing #

If you prefer parsing the page source directly, BeautifulSoup is a fantastic library for HTML manipulation. Pair it with Selenium to get the page source:

from selenium import webdriver
from bs4 import BeautifulSoup

driver = webdriver.Chrome()
driver.get('https://mbasic.facebook.com/cheska.cabral.796/friends')

# Get the page source and parse it with BeautifulSoup
page_source = driver.page_source
soup = BeautifulSoup(page_source, 'html.parser')

# Find all <a> tags with class "cf"
target_links = soup.find_all('a', class_='cf')

# Print each full <a> tag HTML
for link in target_links:
    print(str(link))

driver.quit()

Why These Methods Work Better #

• Both approaches handle variations in HTML formatting (like line breaks, extra spaces, or attribute order) that would break regex.
• They're more maintainable—if Facebook tweaks the page slightly (e.g., adds a new attribute to the <a> tag), these methods will still work as long as the cf class remains.

内容的提问来源于stack exchange，提问作者Ben Daggers