本节主要学习python语言中网络相关知识。

一 

主要文件和目录在Urllib的request.py模块下面。其中支持SSL加密方式访问。

下面我们看看其中的主要类和函数吧。

先看看源码吧。

def urlopen(url, data=http://www.mamicode.com/None, timeout=socket._GLOBAL_DEFAULT_TIMEOUT,>

直接利用URLOPEN函数进行web访问，主要传递的关键参数，就是网址的具体URL
import urllib.request

if __name__ == '__main__':
    print('Main Thread Run :', __name__)
    ResponseData = http://www.mamicode.com/urllib.request.urlopen('http://www.baidu.com/robots.txt')>
//注意上面的代码，采用的是UTF-8编码方式，所以对应解码相同。
结果如下
Main Thread Run : __main__
32
User-agent: Baiduspider

Disallow: /baidu

Disallow: /s?

Disallow: /ulink?

Disallow: /link?



User-agent: Googlebot

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: MSNBot

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Baiduspider-image

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: YoudaoBot

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Sogou web spider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Sogou inst spider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Sogou spider2

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Sogou blog

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Sogou News Spider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Sogou Orion spider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: ChinasoSpider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: Sosospider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?





User-agent: yisouspider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: EasouSpider

Disallow: /baidu

Disallow: /s?

Disallow: /shifen/

Disallow: /homepage/

Disallow: /cpro

Disallow: /ulink?

Disallow: /link?



User-agent: *

Disallow: /



Main Thread Exit : __main__

二       
函数urlretrieve可以实现直接传递URL地址读取该web网页内容，并且以本地文件存储。
函数返回值是一个list其中包括两个参数，第一个是本地存储文件名称，第二个是web服务
返回的http响应头
def urlretrieve(url, filename=None, reporthook=None, data=http://www.mamicode.com/None):>
代码测试

import urllib.request

if __name__ == '__main__':
    print('Main Thread Run :', __name__)
    data = http://www.mamicode.com/urllib.request.urlretrieve('http://www.baidu.com/robots.txt', 'robots.txt')>
结果：

Main Thread Run : __main__
--filename--: robots.txt
--response--: Date: Mon, 22 Sep 2014 08:08:05 GMT
Server: Apache
P3P: CP=" OTI DSP COR IVA OUR IND COM "
Set-Cookie: BAIDUID=4FB847BEE916A0F72ABC5093271CD2BC:FG=1; expires=Tue, 22-Sep-15 08:08:05 GMT; max-age=31536000; path=/; domain=.baidu.com; version=1
Last-Modified: Thu, 17 Jul 2014 07:10:38 GMT
ETag: "91e-4fe5e56791780"
Accept-Ranges: bytes
Content-Length: 2334
Vary: Accept-Encoding,User-Agent
Connection: Close
Content-Type: text/plain



Main Thread Exit : __main__


三           
函数request_host解析url中包含的主机地址 传入参数只有一个Request的对象实例
至于Request对象待会介绍。
下面看看该函数源代码
def request_host(request):
    """Return request-host, as defined by RFC 2965.

    Variation from RFC: returned value is lowercased, for convenient
    comparison.

    """
    url = request.full_url
    host = urlparse(url)[1]
    if host == "":
        host = request.get_header("Host", "")

    # remove port, if present
    host = _cut_port_re.sub("", host, 1)
    return host.lower()

测试代码：
import urllib.request

if __name__ == '__main__':
    print('Main Thread Run :', __name__)
    Req = urllib.request.Request('http://www.baidu.com/robots.txt')
    host = urllib.request.request_host(Req)
    print(host)
    print('\nMain Thread Exit :', __name__)
结果：

Main Thread Run : __main__
www.baidu.com

Main Thread Exit : __main__
四  
     下面介绍该模块主要类Request类。注意啊，是大写的R别搞错了。
      先看看源代码
class Request:

    def __init__(self, url, data=None, headers={},
                 origin_req_host=None, unverifiable=False,
                 method=None):
        self.full_url = url
        self.headers = {}
        self.unredirected_hdrs = {}
        self._data = None
        self.data = data
        self._tunnel_host = None
        for key, value in headers.items():
            self.add_header(key, value)
        if origin_req_host is None:
            origin_req_host = request_host(self)
        self.origin_req_host = origin_req_host
        self.unverifiable = unverifiable
        if method:
            self.method = method

    @property
    def full_url(self):
        if self.fragment:
            return '{}#{}'.format(self._full_url, self.fragment)
        return self._full_url

    @full_url.setter
    def full_url(self, url):
        # unwrap('<URL:type://host/path>') --> 'type://host/path'
        self._full_url = unwrap(url)
        self._full_url, self.fragment = splittag(self._full_url)
        self._parse()

    @full_url.deleter
    def full_url(self):
        self._full_url = None
        self.fragment = None
        self.selector = ''

    @property
    def data(self):
        return self._data

    @data.setter
    def data(self, data):
        if data != self._data:
            self._data = data
            # issue 16464
            # if we change data we need to remove content-length header
            # (cause it's most probably calculated for previous value)
            if self.has_header("Content-length"):
                self.remove_header("Content-length")

    @data.deleter
    def data(self):
        self.data = None

    def _parse(self):
        self.type, rest = splittype(self._full_url)
        if self.type is None:
            raise ValueError("unknown url type: %r" % self.full_url)
        self.host, self.selector = splithost(rest)
        if self.host:
            self.host = unquote(self.host)

    def get_method(self):
        """Return a string indicating the HTTP request method."""
        default_method = "POST" if self.data is not None else "GET"
        return getattr(self, 'method', default_method)

    def get_full_url(self):
        return self.full_url

    def set_proxy(self, host, type):
        if self.type == 'https' and not self._tunnel_host:
            self._tunnel_host = self.host
        else:
            self.type= type
            self.selector = self.full_url
        self.host = host

    def has_proxy(self):
        return self.selector == self.full_url

    def add_header(self, key, val):
        # useful for something like authentication
        self.headers[key.capitalize()] = val

    def add_unredirected_header(self, key, val):
        # will not be added to a redirected request
        self.unredirected_hdrs[key.capitalize()] = val

    def has_header(self, header_name):
        return (header_name in self.headers or
                header_name in self.unredirected_hdrs)

    def get_header(self, header_name, default=None):
        return self.headers.get(
            header_name,
            self.unredirected_hdrs.get(header_name, default))

    def remove_header(self, header_name):
        self.headers.pop(header_name, None)
        self.unredirected_hdrs.pop(header_name, None)

    def header_items(self):
        hdrs = self.unredirected_hdrs.copy()
        hdrs.update(self.headers)
        return list(hdrs.items())

类的初始构造化函数

def __init__(self, url, data=http://www.mamicode.com/None, headers={},>注意里面几个关键参数 url 代表你要访问的URL地址，Data代表你要发送的POST数据，
headers表示你需要在http请求头中包含的头部信息字段
method代表使用GET还是POST方法。
默认是POST传递方式

<span style="font-size:12px;">Req = urllib.request.Request('http://www.baidu.com/robots.txt')</span>

创建Request类的对象实例
例如增加一个User-Agent的字段头请求头

USER_AGENT = {'User-Agent':'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.6) Gecko/20091201 Firefox/3.5.6'}

Req= urllib.request.Request(url='http://www.baidu.com/robots.txt‘, headers=USER_AGENT)

修改超时时间
import socket 
socket.setdefaulttimeout(10)#10s

五  
下面介绍代理使用
代理配置和相关地址信息，必须在调用web访问服务之前进行。
使用代码示例如下：
import socket 
import urllib.request

socket.setdefaulttimeout(10)  # 10s
if __name__ == '__main__':
    print('Main Thread Run :', __name__)
    proxy = urllib.request.ProxyHandler({'http':'http://www.baidu.com:8080'})
    opener = urllib.request.build_opener(proxy, urllib.request.HTTPHandler)
    urllib.request.install_opener(opener)
    content = urllib.request.urlopen('http://www.baidu.com/robots.txt').read()
    print('\nMain Thread Exit :', __name__)
六： 错误异常处理
python的网络服务异常处理相关函数和使用。
主要是try和execpt语句块的使用。记住重要一点
python的异常处理语句，最好是一行代码一抛出一捕捉

示例:

    try :
        reqUrl = urllib.request.Request(url='http://www.baidu.com/robots.txt', headers=USER_AGENT)
    except HTTPError:
        print('urllib.error.HTTPError')
    except URLError:
        print('urllib.error.URLError')
    except OSError:
        print('urllib.error.OSError')
    try :
        responseData = http://www.mamicode.com/urllib.request.urlopen(reqUrl)>


七 说明

以上大概是基本的web访问服务函数和类的一些使用方法，当然还有很多方法和函数可以实现相同功能。
根据个人意愿和需求进行调用。还有一个记得本人只是基础学习，整理笔记于此，方便菜鸟和自己后期查阅。
Python个人学习笔记四