爬虫

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。

Requests

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。

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。

例子：

 

#!/usr/bin/env python
# -*- coding: utf-8 -*-

import urllib2, json, cookielib

def urllib2_request(url, method='GET', cookie='', headers={}, data=None):
    """
    :param url: 请求URL
    :param method: 请求方式--GET, POST, DELETE, PUT, HEAD ...
    :param cookie: 要传入的cookie, cookie='k1=v1;k2=v2'
    :param headers: http请求头，headers={'ContentType':'application/json; charset=UTF-8'}
    :param data: 要发送的数据，GET方式需要传入参数，data={'data':'v1'}
    :return: 返回元祖,响应的字符串内容和cookiejar对象
    对于cookiejar对象可以使用for循环访问：
        for ck in cookiejar:
            print(ck.name, ck,value)
    """


    if data:
        data = json.dumps(data)
    cookie_jar = cookielib.CookieJar()
    handler = urllib2.HTTPCookieProcessor(cookie_jar)
    opener = urllib2.build_opener(handler)
    opener.addheaders.append(['Cookie','k1=v1;k2=v2'])
    request = urllib2.Request(url=url,data=data,headers=headers)
    request.get_method = lambda:method
    response = opener.open(request)
    origin = response.read()
    return(origin,cookie_jar)

# GET
result = urllib2_request('http://www.baidu.com/',method='GET')

#POST
result2 = urllib2_request('http://www.baidu.com/',method='POST',data={'k1':'v1'})

#PUT
result2 = urllib2_request('http://www.baidu.com/',method='PUT',data={'k1':'v1'})

 

1、GET请求 

#!/usr/bin/env python
# -*- code: utf-8 -*-


import requests

#requests GET无参请求
ret = requests.get('https://www.baidu.com/')

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)

请求和响应相关均封装在 ret 对象中。

2、POST请求

#!/usr/bin/env python
# -*- code: utf-8 -*-

import requests
import json

# 基本post实例
payload = {'k1':'v1','k2':'v2'}
res = requests.post('http://httpbin.org/post',data=payload)
print(res.text)

# 发送请求头和数据实例
# url = 'https://api.github.com/some/endpoint'
url = 'https://api.github.com/some/endpoint'
payload = {'some':'data'}
headers = {'content-type':'application/json'}
response = requests.post(url, data=json.dumps(payload), headers=headers)
print(response.text)
print(response.cookies)

3、其他请求

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)

 requests模块已经将常用的Http请求方法为用户封装完成，用户直接调用其提供的相应方法即可，其中方法的所有参数有：

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]>
    """

    # By using the 'with' statement we are sure the session is closed, thus we
    # avoid leaving sockets open which can trigger a ResourceWarning in some
    # cases, and look like a memory leak in others.
    with sessions.Session() as session:
        return session.request(method=method, url=url, **kwargs)

 更多requests模块相关的文档见：http://cn.python-requests.org/zh_CN/latest/