爬取百度页面Python代码(爬取百度网页)
求python抓网页的代码
python3.x中使用urllib.request模块来抓取网页代码，通过urllib.request.urlopen函数取网页内容，获取的为数据流，通过read()函数把数字读取出来，再把读取的二进制数据通过decode函数解码（编号可以通过查看网页源代码中meta? http-equiv="content-type" content="text/html;charset=gbk" /得知，如下例中为gbk编码。），这样就得到了网页的源代码。
如下例所示，抓取本页代码：
import?urllib.request
html?=?urllib.request.urlopen('
).read().decode('gbk')?#注意抓取后要按网页编码进行解码
print(html)
以下为urllib.request.urlopen函数说明：
urllib.request.urlopen(url,
data=None, [timeout, ]*, cafile=None, capath=None,
cadefault=False, context=None)
Open the URL url, which can be either a string or a Request object.
data must be a bytes object specifying additional data to be sent to
the server, or None
if no such data is needed. data may also be an iterable object and in
that case Content-Length value must be specified in the headers. Currently HTTP
requests are the only ones that use data; the HTTP request will be a
POST instead of a GET when the data parameter is provided.
data should be a buffer in the standard application/x-www-form-urlencoded format. The urllib.parse.urlencode() function takes a mapping or
sequence of 2-tuples and returns a string in this format. It should be encoded
to bytes before being used as the data parameter. The charset parameter
in Content-Type
header may be used to specify the encoding. If charset parameter is not sent
with the Content-Type header, the server following the HTTP 1.1 recommendation
may assume that the data is encoded in ISO-8859-1 encoding. It is advisable to
use charset parameter with encoding used in Content-Type header with the Request.
urllib.request module uses HTTP/1.1 and includes Connection:close header
in its HTTP requests.
The optional timeout parameter specifies a timeout in seconds for
blocking operations like the connection attempt (if not specified, the global
default timeout setting will be used). This actually only works for HTTP, HTTPS
and FTP connections.
If context is specified, it must be a ssl.SSLContext instance describing the various SSL
options. See HTTPSConnection for more details.
The optional cafile and capath parameters specify a set of
trusted CA certificates for HTTPS requests. cafile should point to a
single file containing a bundle of CA certificates, whereas capath
should point to a directory of hashed certificate files. More information can be
found in ssl.SSLContext.load_verify_locations().
The cadefault parameter is ignored.
For http and https urls, this function returns a http.client.HTTPResponse object which has the
following HTTPResponse
Objects methods.
For ftp, file, and data urls and requests explicitly handled by legacy URLopener and FancyURLopener classes, this function returns a
urllib.response.addinfourl object which can work as context manager and has methods such as
geturl() — return the URL of the resource retrieved,
commonly used to determine if a redirect was followed
info() — return the meta-information of the page, such
as headers, in the form of an email.message_from_string() instance (see Quick
Reference to HTTP Headers)
getcode() – return the HTTP status code of the response.
Raises URLError on errors.
Note that None
may be returned if no handler handles the request (though the default installed
global OpenerDirector uses UnknownHandler to ensure this never happens).
In addition, if proxy settings are detected (for example, when a *_proxy environment
variable like http_proxy is set), ProxyHandler is default installed and makes sure the
requests are handled through the proxy.
The legacy urllib.urlopen function from Python 2.6 and earlier has
been discontinued; urllib.request.urlopen() corresponds to the old
urllib2.urlopen.
Proxy handling, which was done by passing a dictionary parameter to urllib.urlopen, can be
obtained by using ProxyHandler objects.
Changed in version 3.2: cafile
and capath were added.
Changed in version 3.2: HTTPS virtual
hosts are now supported if possible (that is, if ssl.HAS_SNI is true).
New in version 3.2: data can be
an iterable object.
Changed in version 3.3: cadefault
was added.
Changed in version 3.4.3: context
was added.
Python如何爬取百度图片？
几乎所有的网站都会有反爬机制，这就需要在爬取网页时携带一些特殊参数，比如：user-agent、Cookie等等，可以在写代码的时候用工具将所有参数都带上。
如何用python抓取这个网页的内容？
Python实现常规的静态网页抓取时，往往是用urllib2来获取整个HTML页面，然后从HTML文件中逐字查找对应的关键字。如下所示：
复制代码代码如下:
import urllib2
url="网址"
up=urllib2.urlopen(url)#打开目标页面，存入变量up
cont=up.read()#从up中读入该HTML文件
key1='a href="http'#设置关键字1
key2="target"#设置关键字2
pa=cont.find(key1)#找出关键字1的位置
pt=cont.find(key2,pa)#找出关键字2的位置(从字1后面开始查找)
urlx=cont[pa:pt]#得到关键字1与关键字2之间的内容(即想要的数据)
print urlx