urllib
— 按 URL 打开任意资源
¶
注意
The
urllib
module has been split into parts and renamed in Python 3 to
urllib.request
,
urllib.parse
，和
urllib.error
。
2to3
tool will automatically adapt imports when converting your sources to Python 3. Also note that the
urllib.request.urlopen()
function in Python 3 is equivalent to
urllib2.urlopen()
and that
urllib.urlopen()
已被移除。
This module provides a high-level interface for fetching data across the World Wide Web. In particular, the
urlopen()
function is similar to the built-in function
open()
, but accepts Universal Resource Locators (URLs) instead of filenames. Some restrictions apply — it can only open URLs for reading, and no seek operations are available.
另请参阅
The Requests 包 推荐为更高级别的 HTTP 客户端接口。
Changed in version 2.7.9:
For HTTPS URIs,
urllib
performs all the neccessary certificate and hostname checks by default.
警告
For Python versions earlier than 2.7.9, urllib does not attempt to validate the server certificates of HTTPS URIs. Use at your own risk!
urllib.
urlopen
(
url
[
,
data
[
,
proxies
[
,
context
]
]
]
)
¶
Open a network object denoted by a URL for reading. If the URL does not have a scheme identifier, or if it has
file:
as its scheme identifier, this opens a local file (without
通用换行符
); otherwise it opens a socket to a server somewhere on the network. If the connection cannot be made the
IOError
exception is raised. If all went well, a file-like object is returned. This supports the following methods:
read()
,
readline()
,
readlines()
,
fileno()
,
close()
,
info()
,
getcode()
and
geturl()
. It also has proper support for the
iterator
protocol. One caveat: the
read()
method, if the size argument is omitted or negative, may not read until the end of the data stream; there is no good way to determine that the entire stream from a socket has been read in the general case.
Except for the
info()
,
getcode()
and
geturl()
methods, these methods have the same interface as for file objects — see section
文件对象
in this manual. (It is not a built-in file object, however, so it can’t be used at those few places where a true built-in file object is required.)
The
info()
method returns an instance of the class
mimetools.Message
containing meta-information associated with the URL. When the method is HTTP, these headers are those returned by the server at the head of the retrieved HTML page (including Content-Length and Content-Type). When the method is FTP, a Content-Length header will be present if (as is now usual) the server passed back a file length in response to the FTP retrieval request. A Content-Type header will be present if the MIME type can be guessed. When the method is local-file, returned headers will include a Date representing the file’s last-modified time, a Content-Length giving file size, and a Content-Type containing a guess at the file’s type. See also the description of the
mimetools
模块。
The
geturl()
method returns the real URL of the page. In some cases, the HTTP server redirects a client to another URL. The
urlopen()
function handles this transparently, but in some cases the caller needs to know which URL the client was redirected to. The
geturl()
method can be used to get at this redirected URL.
The
getcode()
method returns the HTTP status code that was sent with the response, or
None
if the URL is no HTTP URL.
若
url
使用
http:
scheme identifier, the optional
data
argument may be given to specify a
POST
request (normally the request type is
GET
)。
data
argument must be in standard
application/x-www-form-urlencoded
格式；见
urlencode()
function below.
The
urlopen()
function works transparently with proxies which do not require authentication. In a Unix or Windows environment, set the
http_proxy
，或
ftp_proxy
environment variables to a URL that identifies the proxy server before starting the Python interpreter. For example (the
'%'
is the command prompt):
% http_proxy="http://www.someproxy.com:3128" % export http_proxy % python ...
The
no_proxy
environment variable can be used to specify hosts which shouldn’t be reached via proxy; if set, it should be a comma-separated list of hostname suffixes, optionally with
:port
appended, for example
cern.ch,ncsa.uiuc.edu,some.host:8080
.
In a Windows environment, if no proxy environment variables are set, proxy settings are obtained from the registry’s Internet Settings section.
In a Mac OS X environment,
urlopen()
will retrieve proxy information from the OS X System Configuration Framework, which can be managed with Network System Preferences panel.
Alternatively, the optional
proxies
argument may be used to explicitly specify proxies. It must be a dictionary mapping scheme names to proxy URLs, where an empty dictionary causes no proxies to be used, and
None
(the default value) causes environmental proxy settings to be used as discussed above. For example:
# Use http://www.someproxy.com:3128 for HTTP proxying proxies = {'http': 'http://www.someproxy.com:3128'} filehandle = urllib.urlopen(some_url, proxies=proxies) # Don't use any proxies filehandle = urllib.urlopen(some_url, proxies={}) # Use proxies from environment - both versions are equivalent filehandle = urllib.urlopen(some_url, proxies=None) filehandle = urllib.urlopen(some_url)
Proxies which require authentication for use are not currently supported; this is considered an implementation limitation.
The
context
parameter may be set to a
ssl.SSLContext
instance to configure the SSL settings that are used if
urlopen()
makes a HTTPS connection.
Changed in version 2.3: 添加 proxies 支持。
2.6 版改变：
添加
getcode()
to returned object and support for the
no_proxy
环境变量。
Changed in version 2.7.9: The context parameter was added. All the neccessary certificate and hostname checks are done by default.
Deprecated since version 2.6:
The
urlopen()
function has been removed in Python 3 in favor of
urllib2.urlopen()
.
urllib.
urlretrieve
(
url
[
,
filename
[
,
reporthook
[
,
data
[
,
context
]
]
]
]
)
¶
Copy a network object denoted by a URL to a local file, if necessary. If the URL points to a local file, or a valid cached copy of the object exists, the object is not copied. Return a tuple
(filename, headers)
where
filename
is the local file name under which the object can be found, and
headers
is whatever the
info()
method of the object returned by
urlopen()
returned (for a remote object, possibly cached). Exceptions are the same as for
urlopen()
.
The second argument, if present, specifies the file location to copy to (if absent, the location will be a tempfile with a generated name). The third argument, if present, is a callable that will be called once on establishment of the network connection and once after each block read thereafter. The callable will be passed three arguments; a count of blocks transferred so far, a block size in bytes, and the total size of the file. The third argument may be
-1
on older FTP servers which do not return a file size in response to a retrieval request.
若
url
使用
http:
scheme identifier, the optional
data
argument may be given to specify a
POST
request (normally the request type is
GET
)。
data
argument must in standard
application/x-www-form-urlencoded
格式；见
urlencode()
function below.
The
context
parameter may be set to a
ssl.SSLContext
instance to configure the SSL settings that are used if
urlretrieve()
makes a HTTPS connection.
Changed in version 2.5:
urlretrieve()
会引发
ContentTooShortError
when it detects that the amount of data available was less than the expected amount (which is the size reported by a
Content-Length
header). This can occur, for example, when the download is interrupted.
The
Content-Length
is treated as a lower bound: if there’s more data to read,
urlretrieve()
reads more data, but if less data is available, it raises the exception.
You can still retrieve the downloaded data in this case, it is stored in the
content
attribute of the exception instance.
若无
Content-Length
header was supplied,
urlretrieve()
can not check the size of the data it has downloaded, and just returns it. In this case you just have to assume that the download was successful.
Changed in version 2.7.9: The context parameter was added. All the neccessary certificate and hostname checks are done by default.
urllib.
_urlopener
¶
The public functions
urlopen()
and
urlretrieve()
create an instance of the
FancyURLopener
class and use it to perform their requested actions. To override this functionality, programmers can create a subclass of
URLopener
or
FancyURLopener
, then assign an instance of that class to the
urllib._urlopener
variable before calling the desired function. For example, applications may want to specify a different
User-Agent
header than
URLopener
defines. This can be accomplished with the following code:
import urllib class AppURLopener(urllib.FancyURLopener): version = "App/1.7" urllib._urlopener = AppURLopener()
urllib.
urlcleanup
(
)
¶
Clear the cache that may have been built up by previous calls to
urlretrieve()
.
urllib.
quote
(
string
[
,
safe
]
)
¶
替换特殊字符在
string
使用
%xx
转义。字母、数字及字符
'_.-'
are never quoted. By default, this function is intended for quoting the path section of the URL. The optional
safe
parameter specifies additional characters that should not be quoted — its default value is
'/'
.
范例：
quote('/~connolly/')
产生
'/%7econnolly/'
.
urllib.
quote_plus
(
string
[
,
safe
]
)
¶
像
quote()
, but also replaces spaces by plus signs, as required for quoting HTML form values when building up a query string to go into a URL. Plus signs in the original string are escaped unless they are included in
safe
。它也没有
safe
默认为
'/'
.
urllib.
unquote
(
string
)
¶
替换
%xx
escapes by their single-character equivalent.
范例：
unquote('/%7Econnolly/')
产生
'/~connolly/'
.
urllib.
unquote_plus
(
string
)
¶
像
unquote()
, but also replaces plus signs by spaces, as required for unquoting HTML form values.
urllib.
urlencode
(
query
[
,
doseq
]
)
¶
Convert a mapping object or a sequence of two-element tuples to a “percent-encoded” string, suitable to pass to
urlopen()
above as the optional
data
argument. This is useful to pass a dictionary of form fields to a
POST
request. The resulting string is a series of
key=value
pairs separated by
'&'
characters, where both
key
and
value
are quoted using
quote_plus()
above. When a sequence of two-element tuples is used as the
query
argument, the first element of each tuple is a key and the second is a value. The value element in itself can be a sequence and in that case, if the optional parameter
doseq
is evaluates to
True
, individual
key=value
pairs separated by
'&'
are generated for each element of the value sequence for the key. The order of parameters in the encoded string will match the order of parameter tuples in the sequence. The
urlparse
module provides the functions
parse_qs()
and
parse_qsl()
which are used to parse query strings into Python data structures.
urllib.
pathname2url
(
path
)
¶
转换路径名
path
from the local syntax for a path to the form used in the path component of a URL. This does not produce a complete URL. The return value will already be quoted using the
quote()
函数。
urllib.
url2pathname
(
path
)
¶
转换路径组件
path
from a percent-encoded URL to the local syntax for a path. This does not accept a complete URL. This function uses
unquote()
以解码
path
.
urllib.
getproxies
(
)
¶
This helper function returns a dictionary of scheme to proxy server URL mappings. It scans the environment for variables named
<scheme>_proxy
, in case insensitive way, for all operating systems first, and when it cannot find it, looks for proxy information from Mac OSX System Configuration for Mac OS X and Windows Systems Registry for Windows. If both lowercase and uppercase environment variables exist (and disagree), lowercase is preferred.
注意
若环境变量
REQUEST_METHOD
is set, which usually indicates your script is running in a CGI environment, the environment variable
HTTP_PROXY
(uppercase
_PROXY
) will be ignored. This is because that variable can be injected by a client using the “Proxy:” HTTP header. If you need to use an HTTP proxy in a CGI environment, either use
ProxyHandler
explicitly, or make sure the variable name is in lowercase (or at least the
_proxy
后缀)。
注意
urllib also exposes certain utility functions like splittype, splithost and others parsing URL into various components. But it is recommended to use
urlparse
for parsing URLs rather than using these functions directly. Python 3 does not expose these helper functions from
urllib.parse
模块。
urllib.
URLopener
(
[
proxies
[
,
context
[
,
**x509
]
]
]
)
¶
Base class for opening and reading URLs. Unless you need to support opening objects using schemes other than
http:
,
ftp:
，或
file:
, you probably want to use
FancyURLopener
.
默认情况下，
URLopener
class sends a
User-Agent
header of
urllib/VVV
，其中
VVV
是
urllib
version number. Applications can define their own
User-Agent
header by subclassing
URLopener
or
FancyURLopener
and setting the class attribute
version
to an appropriate string value in the subclass definition.
可选
proxies
parameter should be a dictionary mapping scheme names to proxy URLs, where an empty dictionary turns proxies off completely. Its default value is
None
, in which case environmental proxy settings will be used if present, as discussed in the definition of
urlopen()
, above.
The
context
parameter may be a
ssl.SSLContext
instance. If given, it defines the SSL settings the opener uses to make HTTPS connections.
Additional keyword parameters, collected in
x509
, may be used for authentication of the client when using the
https:
scheme. The keywords
key_file
and
cert_file
are supported to provide an SSL key and certificate; both are needed to support client authentication.
URLopener
对象将引发
IOError
异常若服务器返回错误代码。
Changed in version 2.7.9: The context parameter was added. All the neccessary certificate and hostname checks are done by default.
open
(
fullurl
[
,
data
]
)
¶
打开
fullurl
using the appropriate protocol. This method sets up cache and proxy information, then calls the appropriate open method with its input arguments. If the scheme is not recognized,
open_unknown()
被调用。
data
argument has the same meaning as the
data
自变量
urlopen()
.
open_unknown
(
fullurl
[
,
data
]
)
¶
能打开未知 URL 类型的可覆盖接口。
retrieve
(
url
[
,
filename
[
,
reporthook
[
,
data
]
]
]
)
¶
Retrieves the contents of
url
and places it in
filename
. The return value is a tuple consisting of a local filename and either a
mimetools.Message
object containing the response headers (for remote URLs) or
None
(for local URLs). The caller must then open and read the contents of
filename
。若
filename
is not given and the URL refers to a local file, the input filename is returned. If the URL is non-local and
filename
is not given, the filename is the output of
tempfile.mktemp()
with a suffix that matches the suffix of the last path component of the input URL. If
reporthook
is given, it must be a function accepting three numeric parameters. It will be called after each chunk of data is read from the network.
reporthook
is ignored for local URLs.
若
url
使用
http:
scheme identifier, the optional
data
argument may be given to specify a
POST
request (normally the request type is
GET
)。
data
argument must in standard
application/x-www-form-urlencoded
格式；见
urlencode()
function below.
version
¶
Variable that specifies the user agent of the opener object. To get
urllib
to tell servers that it is a particular user agent, set this in a subclass as a class variable or in the constructor before calling the base constructor.
urllib.
FancyURLopener
(
...
)
¶
FancyURLopener
子类
URLopener
providing default handling for the following HTTP response codes: 301, 302, 303, 307 and 401. For the 30x response codes listed above, the
定位
header is used to fetch the actual URL. For 401 response codes (authentication required), basic HTTP authentication is performed. For the 30x response codes, recursion is bounded by the value of the
maxtries
attribute, which defaults to 10.
对于所有其它响应代码，方法
http_error_default()
is called which you can override in subclasses to handle the error appropriately.
注意
According to the letter of
RFC 2616
, 301 and 302 responses to POST requests must not be automatically redirected without confirmation by the user. In reality, browsers do allow automatic redirection of these responses, changing the POST to a GET, and
urllib
reproduces this behaviour.
The parameters to the constructor are the same as those for
URLopener
.
注意
当履行基本身份验证时，
FancyURLopener
实例调用其
prompt_user_passwd()
method. The default implementation asks the users for the required information on the controlling terminal. A subclass may override this method to support more appropriate behavior if needed.
The
FancyURLopener
class offers one additional method that should be overloaded to provide the appropriate behavior:
prompt_user_passwd
(
host
,
realm
)
¶
Return information needed to authenticate the user at the given host in the specified security realm. The return value should be a tuple,
(user,
password)
, which can be used for basic authentication.
The implementation prompts for this information on the terminal; an application should override this method to use an appropriate interaction model in the local environment.
urllib.
ContentTooShortError
(
msg
[
,
content
]
)
¶
此异常被引发当
urlretrieve()
function detects that the amount of the downloaded data is less than the expected amount (given by the
Content-Length
header). The
content
attribute stores the downloaded (and supposedly truncated) data.
2.5 版新增。
urllib
限定
¶
Currently, only the following protocols are supported: HTTP, (versions 0.9 and 1.0), FTP, and local files.
缓存特征的
urlretrieve()
has been disabled until I find the time to hack proper processing of Expiration time headers.
应该有函数去查询特定 URL 是否在缓存中。
For backward compatibility, if a URL appears to point to a local file but the file can’t be opened, the URL is re-interpreted using the FTP protocol. This can sometimes cause confusing error messages.
The
urlopen()
and
urlretrieve()
functions can cause arbitrarily long delays while waiting for a network connection to be set up. This means that it is difficult to build an interactive Web client using these functions without using threads.
返回的数据通过
urlopen()
or
urlretrieve()
is the raw data returned by the server. This may be binary data (such as an image), plain text or (for example) HTML. The HTTP protocol provides type information in the reply header, which can be inspected by looking at the
Content-Type
头。若返回的数据是 HTML，可以使用模块
htmllib
去剖析它。
The code handling the FTP protocol cannot differentiate between a file and a directory. This can lead to unexpected behavior when attempting to read a URL that points to a file that is not accessible. If the URL ends in a
/
, it is assumed to refer to a directory and will be handled accordingly. But if an attempt to read a file leads to a 550 error (meaning the URL cannot be found or is not accessible, often for permission reasons), then the path is treated as a directory in order to handle the case when a directory is specified by a URL but the trailing
/
has been left off. This can cause misleading results when you try to fetch a file whose read permissions make it inaccessible; the FTP code will try to read it, fail with a 550 error, and then perform a directory listing for the unreadable file. If fine-grained control is needed, consider using the
ftplib
模块，子类化
FancyURLopener
，或更改
_urlopener
以满足需要。
This module does not support the use of proxies which require authentication. This may be implemented in the future.
Although the
urllib
module contains (undocumented) routines to parse and unparse URL strings, the recommended interface for URL manipulation is in module
urlparse
.
这里是范例会话使用
GET
方法以检索 URL 包含参数：
>>> import urllib >>> params = urllib.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0}) >>> f = urllib.urlopen("http://www.musi-cal.com/cgi-bin/query?%s" % params) >>> print f.read()
以下范例使用
POST
method instead:
>>> import urllib >>> params = urllib.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0}) >>> f = urllib.urlopen("http://www.musi-cal.com/cgi-bin/query", params) >>> print f.read()
The following example uses an explicitly specified HTTP proxy, overriding environment settings:
>>> import urllib >>> proxies = {'http': 'http://proxy.example.com:8080/'} >>> opener = urllib.FancyURLopener(proxies) >>> f = opener.open("http://www.python.org") >>> f.read()
以下范例根本不使用代理，覆盖环境设置：
>>> import urllib >>> opener = urllib.FancyURLopener({}) >>> f = opener.open("http://www.python.org/") >>> f.read()