Python之爬虫

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网络爬虫（又被称为网页蜘蛛，网络机器人，在FOAF社区中间，更经常的称为网页追逐者），是一种按照一定的规则，自动地抓取万维网信息的程序或者脚本。另外一些不常使用的名字还有蚂蚁、自动索引、模拟程序或者蠕虫。

关于Python的爬虫框架Scrapy

请移步至这篇博文——>>> Python爬虫框架——Scrapy

Requests

Python标准库中提供了：urllib、urllib2、httplib等模块以供Http请求，但是，它的 API 太渣了。它是为另一个时代、另一个互联网所创建的。它需要巨量的工作，甚至包括各种方法覆盖，来完成最简单的任务。

Requests 是使用 Apache2 Licensed 许可证的 基于Python开发的HTTP 库，其在Python内置模块的基础上进行了高度的封装，从而使得Pythoner进行网络请求时，变得美好了许多，使用Requests可以轻而易举的完成浏览器可有的任何操作。

1、GET请求

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# 1、无参数实例
   
import requests
   
ret = requests.get(\'https://github.com/timeline.json\')
   
print(ret.url)
print(ret.text)
   
   
# 2、有参数实例
   
import requests
   
payload = {\'key1\': \'value1\', \'key2\': \'value2\'}
ret = requests.get("http://httpbin.org/get", params=payload)
   
print(ret.url)
print(ret.text)

2、POST请求

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# 1、基本POST实例
   
import requests
   
payload = {\'key1\': \'value1\', \'key2\': \'value2\'}
ret = requests.post("http://httpbin.org/post", data=payload)
   
print(ret.text)
   
   
# 2、发送请求头和数据实例
   
import requests
import json
   
url = \'https://api.github.com/some/endpoint\'
payload = {\'some\': \'data\'}
headers = {\'content-type\': \'application/json\'}
   
ret = requests.post(url, data=json.dumps(payload), headers=headers)
   
print(ret.text)
print(ret.cookies)

3、其它请求

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requests.get(url, params=None, **kwargs)
requests.post(url, data=None, json=None, **kwargs)
requests.put(url, data=None, **kwargs)
requests.head(url, **kwargs)
requests.delete(url, **kwargs)
requests.patch(url, data=None, **kwargs)
requests.options(url, **kwargs)
   
# 以上方法均是在此方法的基础上构建
requests.request(method, url, **kwargs)

4、更多参数

def request(method, url, **kwargs):
    """Constructs and sends a :class:`Request <Request>`.

    :param method: method for the new :class:`Request` object.
    :param url: URL for the new :class:`Request` object.
    :param params: (optional) Dictionary or bytes to be sent in the query string for the :class:`Request`.
    :param data: (optional) Dictionary, bytes, or file-like object to send in the body of the :class:`Request`.
    :param json: (optional) json data to send in the body of the :class:`Request`.
    :param headers: (optional) Dictionary of HTTP Headers to send with the :class:`Request`.
    :param cookies: (optional) Dict or CookieJar object to send with the :class:`Request`.
    :param files: (optional) Dictionary of ``\'name\': file-like-objects`` (or ``{\'name\': file-tuple}``) for multipart encoding upload.
        ``file-tuple`` can be a 2-tuple ``(\'filename\', fileobj)``, 3-tuple ``(\'filename\', fileobj, \'content_type\')``
        or a 4-tuple ``(\'filename\', fileobj, \'content_type\', custom_headers)``, where ``\'content-type\'`` is a string
        defining the content type of the given file and ``custom_headers`` a dict-like object containing additional headers
        to add for the file.
    :param auth: (optional) Auth tuple to enable Basic/Digest/Custom HTTP Auth.
    :param timeout: (optional) How long to wait for the server to send data
        before giving up, as a float, or a :ref:`(connect timeout, read
        timeout) <timeouts>` tuple.
    :type timeout: float or tuple
    :param allow_redirects: (optional) Boolean. Set to True if POST/PUT/DELETE redirect following is allowed.
    :type allow_redirects: bool
    :param proxies: (optional) Dictionary mapping protocol to the URL of the proxy.
    :param verify: (optional) whether the SSL cert will be verified. A CA_BUNDLE path can also be provided. Defaults to ``True``.
    :param stream: (optional) if ``False``, the response content will be immediately downloaded.
    :param cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, (\'cert\', \'key\') pair.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response

    Usage::

      >>> import requests
      >>> req = requests.request(\'GET\', \'http://httpbin.org/get\')
      <Response [200]>
    """
参数列表
def param_method_url():
    # requests.request(method=\'get\', url=\'http://127.0.0.1:8000/test/\')
    # requests.request(method=\'post\', url=\'http://127.0.0.1:8000/test/\')
    pass


def param_param():
    # - 可以是字典
    # - 可以是字符串
    # - 可以是字节（ascii编码以内）

    # requests.request(method=\'get\',
    # url=\'http://127.0.0.1:8000/test/\',
    # params={\'k1\': \'v1\', \'k2\': \'水电费\'})

    # requests.request(method=\'get\',
    # url=\'http://127.0.0.1:8000/test/\',
    # params="k1=v1&k2=水电费&k3=v3&k3=vv3")

    # requests.request(method=\'get\',
    # url=\'http://127.0.0.1:8000/test/\',
    # params=bytes("k1=v1&k2=k2&k3=v3&k3=vv3", encoding=\'utf8\'))

    # 错误
    # requests.request(method=\'get\',
    # url=\'http://127.0.0.1:8000/test/\',
    # params=bytes("k1=v1&k2=水电费&k3=v3&k3=vv3", encoding=\'utf8\'))
    pass


def param_data():
    # 可以是字典
    # 可以是字符串
    # 可以是字节
    # 可以是文件对象

    # requests.request(method=\'POST\',
    # url=\'http://127.0.0.1:8000/test/\',
    # data={\'k1\': \'v1\', \'k2\': \'水电费\'})

    # requests.request(method=\'POST\',
    # url=\'http://127.0.0.1:8000/test/\',
    # data="k1=v1; k2=v2; k3=v3; k3=v4"
    # )

    # requests.request(method=\'POST\',
    # url=\'http://127.0.0.1:8000/test/\',
    # data="k1=v1;k2=v2;k3=v3;k3=v4",
    # headers={\'Content-Type\': \'application/x-www-form-urlencoded\'}
    # )

    # requests.request(method=\'POST\',
    # url=\'http://127.0.0.1:8000/test/\',
    # data=open(\'data_file.py\', mode=\'r\', encoding=\'utf-8\'), # 文件内容是：k1=v1;k2=v2;k3=v3;k3=v4
    # headers={\'Content-Type\': \'application/x-www-form-urlencoded\'}
    # )
    pass


def param_json():
    # 将json中对应的数据进行序列化成一个字符串，json.dumps(...)
    # 然后发送到服务器端的body中，并且Content-Type是 {\'Content-Type\': \'application/json\'}
    requests.request(method=\'POST\',
                     url=\'http://127.0.0.1:8000/test/\',
                     json={\'k1\': \'v1\', \'k2\': \'水电费\'})


def param_headers():
    # 发送请求头到服务器端
    requests.request(method=\'POST\',
                     url=\'http://127.0.0.1:8000/test/\',
                     json={\'k1\': \'v1\', \'k2\': \'水电费\'},
                     headers={\'Content-Type\': \'application/x-www-form-urlencoded\'}
                     )


def param_cookies():
    # 发送Cookie到服务器端
    requests.request(method=\'POST\',
                     url=\'http://127.0.0.1:8000/test/\',
                     data={\'k1\': \'v1\', \'k2\': \'v2\'},
                     cookies={\'cook1\': \'value1\'},
                     )
    # 也可以使用CookieJar（字典形式就是在此基础上封装）
    from http.cookiejar import CookieJar
    from http.cookiejar import Cookie

    obj = CookieJar()
    obj.set_cookie(Cookie(version=0, name=\'c1\', value=\'v1\', port=None, domain=\'\', path=\'/\', secure=False, expires=None,
                          discard=True, comment=None, comment_url=None, rest={\'HttpOnly\': None}, rfc2109=False,
                          port_specified=False, domain_specified=False, domain_initial_dot=False, path_specified=False)
                   )
    requests.request(method=\'POST\',
                     url=\'http://127.0.0.1:8000/test/\',
                     data={\'k1\': \'v1\', \'k2\': \'v2\'},
                     cookies=obj)


def param_files():
    # 发送文件
    # file_dict = {
    # \'f1\': open(\'readme\', \'rb\')
    # }
    # requests.request(method=\'POST\',
    # url=\'http://127.0.0.1:8000/test/\',
    # files=file_dict)

    # 发送文件，定制文件名
    # file_dict = {
    # \'f1\': (\'test.txt\', open(\'readme\', \'rb\'))
    # }
    # requests.request(method=\'POST\',
    # url=\'http://127.0.0.1:8000/test/\',
    # files=file_dict)

    # 发送文件，定制文件名
    # file_dict = {
    # \'f1\': (\'test.txt\', "hahsfaksfa9kasdjflaksdjf")
    # }
    # requests.request(method=\'POST\',
    # url=\'http://127.0.0.1:8000/test/\',
    # files=file_dict)

    # 发送文件，定制文件名
    # file_dict = {
    #     \'f1\': (\'test.txt\', "hahsfaksfa9kasdjflaksdjf", \'application/text\', {\'k1\': \'0\'})
    # }
    # requests.request(method=\'POST\',
    #                  url=\'http://127.0.0.1:8000/test/\',
    #                  files=file_dict)

    pass


def param_auth():
    from requests.auth import HTTPBasicAuth, HTTPDigestAuth

    ret = requests.get(\'https://api.github.com/user\', auth=HTTPBasicAuth(\'wupeiqi\', \'sdfasdfasdf\'))
    print(ret.text)

    # ret = requests.get(\'http://192.168.1.1\',
    # auth=HTTPBasicAuth(\'admin\', \'admin\'))
    # ret.encoding = \'gbk\'
    # print(ret.text)

    # ret = requests.get(\'http://httpbin.org/digest-auth/auth/user/pass\', auth=HTTPDigestAuth(\'user\', \'pass\'))
    # print(ret)
    #


def param_timeout():
    # ret = requests.get(\'http://google.com/\', timeout=1)
    # print(ret)

    # ret = requests.get(\'http://google.com/\', timeout=(5, 1))
    # print(ret)
    pass


def param_allow_redirects():
    ret = requests.get(\'http://127.0.0.1:8000/test/\', allow_redirects=False)
    print(ret.text)


def param_proxies():
    # proxies = {
    # "http": "61.172.249.96:80",
    # "https": "http://61.185.219.126:3128",
    # }

    # proxies = {\'http://10.20.1.128\': \'http://10.10.1.10:5323\'}

    # ret = requests.get("http://www.proxy360.cn/Proxy", proxies=proxies)
    # print(ret.headers)


    # from requests.auth import HTTPProxyAuth
    #
    # proxyDict = {
    # \'http\': \'77.75.105.165\',
    # \'https\': \'77.75.105.165\'
    # }
    # auth = HTTPProxyAuth(\'username\', \'mypassword\')
    #
    # r = requests.get("http://www.google.com", proxies=proxyDict, auth=auth)
    # print(r.text)

    pass


def param_stream():
    ret = requests.get(\'http://127.0.0.1:8000/test/\', stream=True)
    print(ret.content)
    ret.close()

    # from contextlib import closing
    # with closing(requests.get(\'http://httpbin.org/get\', stream=True)) as r:
    # # 在此处理响应。
    # for i in r.iter_content():
    # print(i)


def requests_session():
    import requests

    session = requests.Session()

    ### 1、首先登陆任何页面，获取cookie

    i1 = session.get(url="http://dig.chouti.com/help/service")

    ### 2、用户登陆，携带上一次的cookie，后台对cookie中的 gpsd 进行授权
    i2 = session.post(
        url="http://dig.chouti.com/login",
        data={
            \'phone\': "8615131255089",
            \'password\': "xxxxxx",
            \'oneMonth\': ""
        }
    )

    i3 = session.post(
        url="http://dig.chouti.com/link/vote?linksId=8589623",
    )
    print(i3.text)
参数示例

官方文档：http://cn.python-requests.org/zh_CN/latest/user/quickstart.html#id4

BeautifulSoup

BeautifulSoup是一个模块，该模块用于接收一个HTML或XML字符串，然后将其进行格式化，之后遍可以使用他提供的方法进行快速查找指定元素，从而使得在HTML或XML中查找指定元素变得简单。

# 安装  pip3 install beautifulsoup4
from bs4 import BeautifulSoup
 
html_doc = """
<html><head><title>The Dormouse\'s story</title></head>
<body>
asdf
    <div class="title">
        <b>The Dormouse\'s story总共</b>
        <h1>f</h1>
    </div>
<div class="story">Once upon a time there were three little sisters; and their names were
    <a  class="sister0" id="link1">Els<span>f</span>ie</a>,
    <a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and
    <a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>;
and they lived at the bottom of a well.</div>
ad<br/>sf
<p class="story">...</p>
</body>
</html>
"""
 
soup = BeautifulSoup(html_doc, features="lxml")
# 找到第一个a标签
tag1 = soup.find(name=\'a\')
# 找到所有的a标签
tag2 = soup.find_all(name=\'a\')
# 找到id＝link2的标签
tag3 = soup.select(\'#link2\')
简单使用

1，name，标签名称

2，attr，标签属性

3，children，所有子标签

4，descendants，所有子子孙孙标签

5，clear,将标签的所有子标签全部清空（保留标签名）

6，decompose,递归的删除所有的标签

7，extract，递归的删除所有的标签，并获取删除的标签

8，decode,转换为字符串（含当前标签）；decode_contents（不含当前标签）

9，encode,转换为字节（含当前标签）；encode_contents（不含当前标签）

10，find,获取匹配的第一个标签

11， find_all,获取匹配的所有标签