使用 python 抓取网页中的“AttributeError”

Question

当我使用 Jupyter 在笔记本电脑上执行相同的代码时，出现以下错误

AttributeError 
Traceback (most recent call last) in # form cycles) 
   excludedPages = filter(isInternalNode, getChildren("http://www.quora.com/directory")) 
-->excludedPages.append("http://www.quora.com") 
   excludedPages.append("http://www.quora.com#")    
   excludedPages.append("http://www.quora.com/") 
AttributeError: 'filter' object has no attribute 'append'

代码在这里-https://github.com/jessicatysu/quora/blob/master/numfollowers.py

Answer 1

此代码适用于 Python 2 - 您可以看到 print 没有 ()，它仅适用于 Python 2。

但 Python 2 也有其他不同之处。在 Python 2 中 filter() 创建 list 但在 Python 3 中 filter() 是“惰性的”，它不会立即创建列表，在某些情况下您必须使用 list() 将 filter() 转换为 list

而且你必须在使用append()之前这样做

excludedPages = list(filter(...))

---

编辑：

这是运行没有错误的代码。

在代码中，您可以查看 cmets # changed 的更多信息。

但问题是这个脚本已有 7 年历史（从 2013 年开始）并且Quora 更改了 HTML：

• 起始页 /directory 不显示用户列表
  （可能是为了安全或GDPRGeneral Data Protection Regulation）
• 它使用 JavaScript 但mechanize 无法运行 JavaScript

所以代码没用:)

您必须使用Selenium 来控制可以运行JavaScript 的真实网络浏览器。而且您必须分析网页以创建新代码。

# Grabs N people randomly from the directory using reservoir sampling, then
# counts the number of followers they have.  I never got to run this script
# to completion because Quora blocked the script before I added the rate
# limits.

import mechanize
import random
import http.cookiejar as cookielib  # changed: in Python 3 module `cookielib` was renamed to `http.cookiejar`
import re
from time import sleep

NUM_SAMPLES = 1000
FOLLOWERS_FILE = "followers.txt"
USERS_FILE = "users.txt"
ERR_LOG = "errors.txt"

err = open(ERR_LOG, 'w')

# Randomly chosen Quora users (written in the form of links to Quora
# profiles)
users = []
curUserIdx = 1

# Regular expressions that will be used multiple times
leaf = re.compile("-") # Separator between first and last names!
internalNode = re.compile("directory/page")
fnum = re.compile("Followers.*>([0-9]+)<.*Following")

# We use this function to open pages instead of br.open to avoid putting a
# high load on Quora's servers.  This means the script takes a lot longer
# though - estimated time 1 day for 2 million users.  (21400 page accesses
# * 4 seconds per access = 23.8 hours.)
def openPage(site):
    print('[DEBUG] openPage:', site)  # changed: add only for debug 
    result = br.open(site)  # changed: add `result =`
    sleep(3)
    return result  # changed: add `return result`

# Gets child links
def getChildren(node):
    try:
        openPage(node)
        print(br.links())
        return ["http://www.quora.com" + link.url for link in br.links()]
    except:
        print("Could not get children of " + node)
        err.write("Could not get children of " + node)
        return []

# Checks to see if the link is a user profile.
def isLeaf(node):
    return leaf.search(node)

# Checks to see if the link is an intermediate node in the directory.
def isInternalNode(node):
    return internalNode.search(node)

# Checks to see if the page is part of the people directory
def inPeopleDirectory(node):
    try:
        page = openPage(node)
        html = page.read()
    except Exception as ex:  # changed: display some info about problem
        print('ex:', ex)     # changed: display some info about problem
        print("Could not open site " + node)
        err.write("Could not open site " + node)
        return False

    # --- change : add decode with try/except ---
    try:
        html = html.decode('utf-8')
    except:
        print("Could not decode HTML using UTF-8 " + node)
        err.write("Could not decode HTML using UTF-8 " + node)
        return False
    # --- change : end ---

    return "People on Quora" in html

# Applies reservoir sampling to a candidate leaf
def sample(node):
    # curUserIdx is 1-indexed
    global users, curUserIdx
    # Initialize the list
    if (curUserIdx <= NUM_SAMPLES):
        users.append(node)

    # Replace elements
    else:
        # random.randint chooses a random integer, inclusive
        choice = random.randint(1, curUserIdx)
        if (choice <= NUM_SAMPLES):
            users[choice - 1] = node
    curUserIdx += 1

# Gets the number of followers for a user
def getFollowers(profile):
    try:
        page = openPage(profile)
        m = fnum.search(page.read())
        if m:
            return m.group(1)
    except:
        print("Could not get number of followers for " + profile)
        err.write("Could not get number of followers for " + profile)

# Traverses the tree using depth first search.
def crawl(node):
    for child in getChildren(node):
        if child in excludedPages:
            pass
        elif isLeaf(child):
            print("Sampling " + child)
            sample(child)
        elif isInternalNode(child):
            print("Crawling internal node " + child)
            crawl(child)
        else:
            print("Passing on link " + child)

# Initialize browser

br = mechanize.Browser()

cj = cookielib.LWPCookieJar()
br.set_cookiejar(cj)

br.set_handle_equiv(True)
br.set_handle_gzip(True)
br.set_handle_redirect(True)
br.set_handle_referer(True)
br.set_handle_robots(False)

# Follows refresh 0 but not hangs on refresh > 0
br.set_handle_refresh(mechanize._http.HTTPRefreshProcessor(), max_time=1)

# User-Agent
br.addheaders = [('User-agent', 'Mozilla/5.0 (X11; U; Linux i686; en-US; \
rv:1.9.0.1) Gecko/2008071615 Fedora/3.0.1-1.fc9 Firefox/3.0.1')]

# Get list of top level pages (and exclude them from searches, because they
# form cycles)
excludedPages = list(filter(isInternalNode, getChildren("https://www.quora.com/directory")))  # changed: add `list()`
excludedPages.append("https://www.quora.com")
excludedPages.append("https://www.quora.com#")
excludedPages.append("https://www.quora.com/")
excludedPages.append("https://www.quora.com/about/tos")
print('[DEBUG] topPages:', list(excludedPages))  # changed: add only for debug 

topPages = filter(inPeopleDirectory, excludedPages)
print('[DEBUG] topPages:', list(topPages))  # changed: add only for debug

# Access Quora directory (it's public access!)
for page in topPages:
    crawl(page)

# Get followers for each user
ff = open(FOLLOWERS_FILE, 'w')
uf = open(USERS_FILE, 'w')

# Write these in two separate steps in case something goes wrong with
# getFollowers.  I don't want to lose my random sample, because that is the
# hardest part to get.
for u in users:
    uf.write(u + "\n")
uf.close()

for u in users:
    numFollowers = getFollowers(u)
    if numFollowers:
        ff.write(u + "\t" + getFollowers(u) + "\n")

ff.close()
err.close()