21.6. urllib.request — 用于打开 URL 的可扩展库 ¶

The urllib.request 模块定义有助于在复杂环境打开 URL (主要是 HTTP) 的函数和类 — 基本和摘要身份验证、重定向、Cookie 等。

另请参阅

The Requests 包 is recommended for a higher-level http client interface.

The urllib.request 模块定义了下列函数：

urllib.request. urlopen ( url , data=None , [ timeout , ] * , cafile=None , capath=None , cadefault=False , context=None ) ¶

打开 URL url ，其可以是字符串或 Request 对象。

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 应该是缓冲，采用标准 application/x-www-form-urlencoded 格式。 urllib.parse.urlencode() function takes a mapping or sequence of 2-tuples and returns an ASCII text string in this format. It should be encoded to bytes before being used as the data 参数。

urllib.request 模块使用 HTTP/1.1 并包括 Connection:close HTTP 头在其 HTTP 请求中。

可选 timeout 参数指定超时 (以秒为单位) 为阻塞像连接尝试操作 (若未指定，将使用全局默认超时设置)。这实际仅工作于 HTTP HTTPS 及 FTP 连接。

若 context 被指定，它必须是 ssl.SSLContext 实例 (描述各种 SSL 选项)。见 HTTPSConnection 了解更多细节。

可选 cafile and capath 参数为 HTTPS 请求指定一组受信任的 CA 证书。 cafile 应该指向包含一捆 CA 证书的单个文件，而 capath 应该指向哈希证书文件目录。可以找到更多信息在 ssl.SSLContext.load_verify_locations() .

The cadefault 参数被忽略。

This function always returns an object which can work as 上下文管理器 并具有如下方法

• 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() 实例 (见 快速参考 HTTP 头 )
• getcode() – 返回 HTTP 响应状态码。

For http and https urls, this function returns a http.client.HTTPResponse 稍微修改对象。除上述 3 新方法外，msg 属性包含的信息如同 reason 属性 — 由服务器返回的原因短语 — 而不是在文档编制中指定的响应 Header 头为 HTTPResponse .

For ftp, file, and data urls and requests explicitly handled by legacy URLopener and FancyURLopener 类，此函数返回 urllib.response.addinfourl 对象。

引发 URLError on errors.

注意， None 可能被返回，若没有处理程序处理请求 (虽然默认安装了全局 OpenerDirector 使用 UnknownHandler 以确保这从不发生)。

此外，若检测到代理设置 (例如，当 *_proxy 环境变量像 http_proxy 有设置)， ProxyHandler ProxyHandler 是默认安装的，并确保透过代理处理请求。

传统 urllib.urlopen 函数从 Python 2.6 及更早版本起已被放弃； urllib.request.urlopen() 相当于旧 urllib2.urlopen 。处理代理是把字典参数传递给 urllib.urlopen ，可以获得通过使用 ProxyHandler 对象。

3.2 版改变： cafile and capath 被添加。

3.2 版改变： 现在支持 HTTPS 虚拟主机，若可能的话 (也就是说，若 ssl.HAS_SNI 为 True)。

3.2 版新增： data 可以是可迭代对象。

3.3 版改变： cadefault 被添加。

3.4.3 版改变： context 被添加。

urllib.request. install_opener ( opener ) ¶

安装 OpenerDirector instance as the default global opener. Installing an opener is only necessary if you want urlopen to use that opener; otherwise, simply call OpenerDirector.open() 而不是 urlopen() . The code does not check for a real OpenerDirector , and any class with the appropriate interface will work.

urllib.request. build_opener ( [ handler , ... ] ) ¶

返回 OpenerDirector instance, which chains the handlers in the order given. handler s can be either instances of BaseHandler , or subclasses of BaseHandler (in which case it must be possible to call the constructor without any parameters). Instances of the following classes will be in front of the handler s, unless the handler s contain them, instances of them or subclasses of them: ProxyHandler (if proxy settings are detected), UnknownHandler , HTTPHandler , HTTPDefaultErrorHandler , HTTPRedirectHandler , FTPHandler , FileHandler , HTTPErrorProcessor .

若 Python 安装有 SSL 支持 (即：若 ssl 模块可以被导入)， HTTPSHandler will also be added.

A BaseHandler 子类还可以改变其 handler_order attribute to modify its position in the handlers list.

urllib.request. 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.request. 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.request. getproxies ( ) ¶

This helper function returns a dictionary of scheme to proxy server URL mappings. It scans the environment for variables named <scheme>_proxy , in a case insensitive approach, 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.

提供了下列类：

class urllib.request. Request ( url , data=None , headers={} , origin_req_host=None , unverifiable=False , method=None ) ¶

此类是 URL 请求的抽象。

url 应是包含有效 URL 的字符串。

data must be a bytes object specifying additional data to send to the server, or None 若不需要这样的数据。目前，仅 HTTP 请求使用 data ; the HTTP request will be a POST instead of a GET when the data parameter is provided. data 应该是缓冲，采用标准 application/x-www-form-urlencoded 格式。 urllib.parse.urlencode() function takes a mapping or sequence of 2-tuples and returns an ASCII string in this format. It should be encoded to bytes before being used as the data 参数。

headers should be a dictionary, and will be treated as if add_header() was called with each key and value as arguments. This is often used to “spoof” the User-Agent header, which is used by a browser to identify itself – some HTTP servers only allow requests coming from common browsers as opposed to scripts. For example, Mozilla Firefox may identify itself as "Mozilla/5.0 (X11; U; Linux i686) Gecko/20071127 Firefox/2.0.0.11" ，而 urllib ‘s default user agent string is "Python-urllib/2.6" (在 Python 2.6)。

An example of using Content-Type header with data argument would be sending a dictionary like {"Content-Type": "application/x-www-form-urlencoded"} .

最后 2 自变量仅对正确处理第 3 方 HTTP Cookie 感兴趣：

origin_req_host 应该是原始事务请求主机，作为定义通过 RFC 2965 。默认为 http.cookiejar.request_host(self) . This is the host name or IP address of the original request that was initiated by the user. For example, if the request is for an image in an HTML document, this should be the request-host of the request for the page containing the image.

unverifiable should indicate whether the request is unverifiable, as defined by RFC 2965. It defaults to False . An unverifiable request is one whose URL the user did not have the option to approve. For example, if the request is for an image in an HTML document, and the user had no option to approve the automatic fetching of the image, this should be true.

方法 应该是指示将使用的 HTTP 请求方法的字符串 (如 'HEAD' )。若提供，其值被存储在 method 属性且被使用通过 get_method() . Subclasses may indicate a default method by setting the method 类本身属性。

3.3 版改变： Request.method 自变量被添加到 Request 类。

3.4 版改变： 默认 Request.method 可能被指示在类级别。

class urllib.request. OpenerDirector ¶

The OpenerDirector 类打开 URL 凭借 BaseHandler s chained together. It manages the chaining of handlers, and recovery from errors.

class urllib.request. BaseHandler ¶

This is the base class for all registered handlers — and handles only the simple mechanics of registration.

class urllib.request. HTTPDefaultErrorHandler ¶

A class which defines a default handler for HTTP error responses; all responses are turned into HTTPError 异常。

class urllib.request. HTTPRedirectHandler ¶

处理重定向的类。

class urllib.request. HTTPCookieProcessor ( cookiejar=None ) ¶

处理 HTTP Cookie 的类。

class urllib.request. ProxyHandler ( proxies=None ) ¶

促使请求透过代理进行。若 proxies is given, it must be a dictionary mapping protocol names to URLs of proxies. The default is to read the list of proxies from the environment variables <protocol>_proxy . If no proxy environment variables are set, then in a Windows environment proxy settings are obtained from the registry’s Internet Settings section, and in a Mac OS X environment proxy information is retrieved from the OS X System Configuration Framework.

要禁用自动检测代理，传递空字典。

class urllib.request. HTTPPasswordMgr ¶

保持数据库的 (realm, uri) -> (user, password) 映射。

class urllib.request. HTTPPasswordMgrWithDefaultRealm ¶

保持数据库的 (realm, uri) -> (user, password) mappings. A realm of None is considered a catch-all realm, which is searched if no other realm fits.

class urllib.request. AbstractBasicAuthHandler ( password_mgr=None ) ¶

This is a mixin class that helps with HTTP authentication, both to the remote host and to a proxy. password_mgr , if given, should be something that is compatible with HTTPPasswordMgr ; refer to section HTTPPasswordMgr 对象 for information on the interface that must be supported.

class urllib.request. HTTPBasicAuthHandler ( password_mgr=None ) ¶

Handle authentication with the remote host. password_mgr , if given, should be something that is compatible with HTTPPasswordMgr ; refer to section HTTPPasswordMgr 对象 for information on the interface that must be supported. HTTPBasicAuthHandler will raise a ValueError when presented with a wrong Authentication scheme.

class urllib.request. ProxyBasicAuthHandler ( password_mgr=None ) ¶

Handle authentication with the proxy. password_mgr , if given, should be something that is compatible with HTTPPasswordMgr ; refer to section HTTPPasswordMgr 对象 for information on the interface that must be supported.

class urllib.request. AbstractDigestAuthHandler ( password_mgr=None ) ¶

This is a mixin class that helps with HTTP authentication, both to the remote host and to a proxy. password_mgr , if given, should be something that is compatible with HTTPPasswordMgr ; refer to section HTTPPasswordMgr 对象 for information on the interface that must be supported.

class urllib.request. HTTPDigestAuthHandler ( password_mgr=None ) ¶

Handle authentication with the remote host. password_mgr , if given, should be something that is compatible with HTTPPasswordMgr ; refer to section HTTPPasswordMgr 对象 for information on the interface that must be supported. When both Digest Authentication Handler and Basic Authentication Handler are both added, Digest Authentication is always tried first. If the Digest Authentication returns a 40x response again, it is sent to Basic Authentication handler to Handle. This Handler method will raise a ValueError when presented with an authentication scheme other than Digest or Basic.

3.3 版改变： 引发 ValueError 当身份验证方案不被支持时。

class urllib.request. ProxyDigestAuthHandler ( password_mgr=None ) ¶

Handle authentication with the proxy. password_mgr , if given, should be something that is compatible with HTTPPasswordMgr ; refer to section HTTPPasswordMgr 对象 for information on the interface that must be supported.

class urllib.request. HTTPHandler ¶

处理打开 HTTP URL 的类。

class urllib.request. HTTPSHandler ( debuglevel=0 , context=None , check_hostname=None ) ¶

A class to handle opening of HTTPS URLs. context and check_hostname 拥有相同含义如在 http.client.HTTPSConnection .

3.2 版改变： context and check_hostname 被添加。

class urllib.request. FileHandler ¶

打开本地文件。

class urllib.request. DataHandler ¶

打开数据 URL。

3.4 版新增。

class urllib.request. FTPHandler ¶

打开 FTP URL。

class urllib.request. CacheFTPHandler ¶

打开 FTP URL，保持打开 FTP 连接的缓存以最小化延迟。

class urllib.request. UnknownHandler ¶

A catch-all class to handle unknown URLs.

class urllib.request. HTTPErrorProcessor ¶

处理 HTTP 错误响应。

21.6.1. 请求对象 ¶

以下方法描述 Request ‘s public interface, and so all may be overridden in subclasses. It also defines several public attributes that can be used by clients to inspect the parsed request.

Request. full_url ¶

被传递给构造函数的原始 URL。

3.4 版改变。

Request.full_url is a property with setter, getter and a deleter. Getting full_url returns the original request URL with the fragment, if it was present.

Request. type ¶

URI 方案。

Request. host ¶

The URI authority, typically a host, but may also contain a port separated by a colon.

Request. origin_req_host ¶

The original host for the request, without port.

Request. 选择器 ¶

URI 路径。若 Request uses a proxy, then selector will be the full url that is passed to the proxy.

Request. data ¶

The entity body for the request, or None if not specified.

3.4 版改变： Changing value of Request.data now deletes “Content-Length” header if it was previously set or calculated.

Request. unverifiable ¶

boolean, indicates whether the request is unverifiable as defined by RFC 2965.

Request. 方法 ¶

The HTTP request method to use. By default its value is None , which means that get_method() will do its normal computation of the method to be used. Its value can be set (thus overriding the default computation in get_method() ) either by providing a default value by setting it at the class level in a Request subclass, or by passing a value in to the Request constructor via the 方法 自变量。

3.3 版新增。

3.4 版改变： A default value can now be set in subclasses; previously it could only be set via the constructor argument.

Request. get_method ( ) ¶

Return a string indicating the HTTP request method. If Request.method 不是 None , return its value, otherwise return 'GET' if Request.data is None ，或 'POST' if it’s not. This is only meaningful for HTTP requests.

3.3 版改变： get_method 现在查看值对于 Request.method .

Request. add_header ( key , val ) ¶

Add another header to the request. Headers are currently ignored by all handlers except HTTP handlers, where they are added to the list of headers sent to the server. Note that there cannot be more than one header with the same name, and later calls will overwrite previous calls in case the key collides. Currently, this is no loss of HTTP functionality, since all headers which have meaning when used more than once have a (header-specific) way of gaining the same functionality using only one header.

Request. add_unredirected_header ( key , header ) ¶

添加不会被添加到重定向请求的 Header 头。

Request. has_header ( header ) ¶

Return whether the instance has the named header (checks both regular and unredirected).

Request. remove_header ( header ) ¶

Remove named header from the request instance (both from regular and unredirected headers).

3.4 版新增。

Request. get_full_url ( ) ¶

返回在构造函数中给定的 URL。

3.4 版改变。

返回 Request.full_url

Request. set_proxy ( host , type ) ¶

Prepare the request by connecting to a proxy server. The host and type will replace those of the instance, and the instance’s selector will be the original URL given in the constructor.

Request. get_header ( header_name , default=None ) ¶

Return the value of the given header. If the header is not present, return the default value.

Request. header_items ( ) ¶

Return a list of tuples (header_name, header_value) of the Request headers.

3.4 版改变： The request methods add_data, has_data, get_data, get_type, get_host, get_selector, get_origin_req_host and is_unverifiable that were deprecated since 3.3 have been removed.

21.6.2. OpenerDirector 对象 ¶

OpenerDirector 实例具有下列方法：

OpenerDirector. add_handler ( handler ) ¶

handler should be an instance of BaseHandler . The following methods are searched, and added to the possible chains (note that HTTP errors are a special case).

• protocol_open() — signal that the handler knows how to open protocol URLs.
• http_error_type() — signal that the handler knows how to handle HTTP errors with HTTP error code type .
• protocol_error() — signal that the handler knows how to handle errors from (non- http ) protocol .
• protocol_request() — signal that the handler knows how to pre-process protocol requests.
• protocol_response() — signal that the handler knows how to post-process protocol responses.

OpenerDirector. open ( url , data=None [ , timeout ] ) ¶

打开给定 url (which can be a request object or a string), optionally passing the given data . Arguments, return values and exceptions raised are the same as those of urlopen() (which simply calls the open() method on the currently installed global OpenerDirector ). 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). The timeout feature actually works only for HTTP, HTTPS and FTP connections).

OpenerDirector. error ( proto , *args ) ¶

Handle an error of the given protocol. This will call the registered error handlers for the given protocol with the given arguments (which are protocol specific). The HTTP protocol is a special case which uses the HTTP response code to determine the specific error handler; refer to the http_error_*() methods of the handler classes.

Return values and exceptions raised are the same as those of urlopen() .

OpenerDirector 对象按 3 阶段打开 URL：

The order in which these methods are called within each stage is determined by sorting the handler instances.

1. Every handler with a method named like protocol_request() has that method called to pre-process the request.

2. Handlers with a method named like protocol_open() are called to handle the request. This stage ends when a handler either returns a non- None value (ie. a response), or raises an exception (usually URLError ). Exceptions are allowed to propagate.

   In fact, the above algorithm is first tried for methods named default_open() . If all such methods return None , the algorithm is repeated for methods named like protocol_open() . If all such methods return None , the algorithm is repeated for methods named unknown_open() .

   Note that the implementation of these methods may involve calls of the parent OpenerDirector instance’s open() and error() 方法。

3. Every handler with a method named like protocol_response() has that method called to post-process the response.

21.6.3. BaseHandler 对象 ¶

BaseHandler objects provide a couple of methods that are directly useful, and others that are meant to be used by derived classes. These are intended for direct use:

BaseHandler. add_parent ( director ) ¶

Add a director as parent.

BaseHandler. close ( ) ¶

移除任何父级。

The following attribute and methods should only be used by classes derived from BaseHandler .

注意

The convention has been adopted that subclasses defining protocol_request() or protocol_response() methods are named *Processor ; all others are named *Handler .

BaseHandler. parent ¶

有效 OpenerDirector , which can be used to open using a different protocol, or handle errors.

BaseHandler. default_open ( req ) ¶

This method is not defined in BaseHandler , but subclasses should define it if they want to catch all URLs.

This method, if implemented, will be called by the parent OpenerDirector . It should return a file-like object as described in the return value of the open() of OpenerDirector ，或 None . It should raise URLError , unless a truly exceptional thing happens (for example, MemoryError should not be mapped to URLError ).

This method will be called before any protocol-specific open method.

BaseHandler. protocol_open ( req )

This method is not defined in BaseHandler , but subclasses should define it if they want to handle URLs with the given protocol.

This method, if defined, will be called by the parent OpenerDirector . Return values should be the same as for default_open() .

BaseHandler. unknown_open ( req ) ¶

This method is not defined in BaseHandler , but subclasses should define it if they want to catch all URLs with no specific registered handler to open it.

This method, if implemented, will be called by the parent OpenerDirector . Return values should be the same as for default_open() .

BaseHandler. http_error_default ( req , fp , code , msg , hdrs ) ¶

This method is not defined in BaseHandler , but subclasses should override it if they intend to provide a catch-all for otherwise unhandled HTTP errors. It will be called automatically by the OpenerDirector getting the error, and should not normally be called in other circumstances.

req 将是 Request 对象， fp will be a file-like object with the HTTP error body, code will be the three-digit code of the error, msg will be the user-visible explanation of the code and hdrs will be a mapping object with the headers of the error.

Return values and exceptions raised should be the same as those of urlopen() .

BaseHandler. http_error_nnn ( req , fp , code , msg , hdrs ) ¶

nnn should be a three-digit HTTP error code. This method is also not defined in BaseHandler , but will be called, if it exists, on an instance of a subclass, when an HTTP error with code nnn 出现。

Subclasses should override this method to handle specific HTTP errors.

Arguments, return values and exceptions raised should be the same as for http_error_default() .

BaseHandler. protocol_request ( req )

This method is not defined in BaseHandler , but subclasses should define it if they want to pre-process requests of the given protocol.

This method, if defined, will be called by the parent OpenerDirector . req 将是 Request object. The return value should be a Request 对象。

BaseHandler. protocol_response ( req , response )

This method is not defined in BaseHandler , but subclasses should define it if they want to post-process responses of the given protocol.

This method, if defined, will be called by the parent OpenerDirector . req 将是 Request 对象。 response will be an object implementing the same interface as the return value of urlopen() . The return value should implement the same interface as the return value of urlopen() .

21.6.4. HTTPRedirectHandler 对象 ¶

注意

Some HTTP redirections require action from this module’s client code. If this is the case, HTTPError 被引发。见 RFC 2616 for details of the precise meanings of the various redirection codes.

An HTTPError exception raised as a security consideration if the HTTPRedirectHandler is presented with a redirected url which is not an HTTP, HTTPS or FTP url.

HTTPRedirectHandler. redirect_request ( req , fp , code , msg , hdrs , newurl ) ¶

返回 Request or None in response to a redirect. This is called by the default implementations of the http_error_30*() methods when a redirection is received from the server. If a redirection should take place, return a new Request to allow http_error_30*() to perform the redirect to newurl . Otherwise, raise HTTPError if no other handler should try to handle this URL, or return None if you can’t but another handler might.

注意

The default implementation of this method does not strictly follow RFC 2616 , which says that 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 the default implementation reproduces this behavior.

HTTPRedirectHandler. http_error_301 ( req , fp , code , msg , hdrs ) ¶

重定向到 Location: or URI: URL. This method is called by the parent OpenerDirector when getting an HTTP ‘moved permanently’ response.

HTTPRedirectHandler. http_error_302 ( req , fp , code , msg , hdrs ) ¶

如同 http_error_301() , but called for the ‘found’ response.

HTTPRedirectHandler. http_error_303 ( req , fp , code , msg , hdrs ) ¶

如同 http_error_301() , but called for the ‘see other’ response.

HTTPRedirectHandler. http_error_307 ( req , fp , code , msg , hdrs ) ¶

如同 http_error_301() , but called for the ‘temporary redirect’ response.

21.6.5. HTTPCookieProcessor 对象 ¶

HTTPCookieProcessor 实例有一属性：

HTTPCookieProcessor. cookiejar ¶

The http.cookiejar.CookieJar 在其中存储 Cookie。

21.6.6. ProxyHandler 对象 ¶

ProxyHandler. protocol_open ( request )

The ProxyHandler will have a method protocol_open() for every protocol which has a proxy in the proxies dictionary given in the constructor. The method will modify requests to go through the proxy, by calling request.set_proxy() , and call the next handler in the chain to actually execute the protocol.

21.6.7. HTTPPasswordMgr 对象 ¶

这些方法可用于 HTTPPasswordMgr and HTTPPasswordMgrWithDefaultRealm 对象。

HTTPPasswordMgr. add_password ( realm , uri , user , passwd ) ¶

uri can be either a single URI, or a sequence of URIs. realm , user and passwd must be strings. This causes (user, passwd) to be used as authentication tokens when authentication for realm and a super-URI of any of the given URIs is given.

HTTPPasswordMgr. find_user_password ( realm , authuri ) ¶

Get user/password for given realm and URI, if any. This method will return (None, None) if there is no matching user/password.

For HTTPPasswordMgrWithDefaultRealm 对象，领域 None will be searched if the given realm has no matching user/password.

21.6.8. AbstractBasicAuthHandler Objects ¶

AbstractBasicAuthHandler. http_error_auth_reqed ( authreq , host , req , headers ) ¶

Handle an authentication request by getting a user/password pair, and re-trying the request. authreq should be the name of the header where the information about the realm is included in the request, host specifies the URL and path to authenticate for, req should be the (failed) Request object, and headers should be the error headers.

host is either an authority (e.g. "python.org" ) or a URL containing an authority component (e.g. "http://python.org/" ). In either case, the authority must not contain a userinfo component (so, "python.org" and "python.org:80" are fine, "joe:password@python.org" is not).

21.6.9. HTTPBasicAuthHandler Objects ¶

HTTPBasicAuthHandler. http_error_401 ( req , fp , code , msg , hdrs ) ¶

Retry the request with authentication information, if available.

21.6.10. ProxyBasicAuthHandler Objects ¶

ProxyBasicAuthHandler. http_error_407 ( req , fp , code , msg , hdrs ) ¶

Retry the request with authentication information, if available.

21.6.11. AbstractDigestAuthHandler Objects ¶

AbstractDigestAuthHandler. http_error_auth_reqed ( authreq , host , req , headers ) ¶

authreq should be the name of the header where the information about the realm is included in the request, host should be the host to authenticate to, req should be the (failed) Request object, and headers should be the error headers.

21.6.12. HTTPDigestAuthHandler Objects ¶

HTTPDigestAuthHandler. http_error_401 ( req , fp , code , msg , hdrs ) ¶

Retry the request with authentication information, if available.

21.6.13. ProxyDigestAuthHandler Objects ¶

ProxyDigestAuthHandler. http_error_407 ( req , fp , code , msg , hdrs ) ¶

Retry the request with authentication information, if available.

21.6.14. HTTPHandler Objects ¶

HTTPHandler. http_open ( req ) ¶

Send an HTTP request, which can be either GET or POST, depending on req.has_data() .

21.6.15. HTTPSHandler Objects ¶

HTTPSHandler. https_open ( req ) ¶

Send an HTTPS request, which can be either GET or POST, depending on req.has_data() .

21.6.16. FileHandler Objects ¶

FileHandler. file_open ( req ) ¶

打开本地文件，若没有主机名，或主机名为 'localhost' .

3.2 版改变： This method is applicable only for local hostnames. When a remote hostname is given, an URLError 被引发。

21.6.17. DataHandler Objects ¶

DataHandler. data_open ( req ) ¶

Read a data URL. This kind of URL contains the content encoded in the URL itself. The data URL syntax is specified in RFC 2397 . This implementation ignores white spaces in base64 encoded data URLs so the URL may be wrapped in whatever source file it comes from. But even though some browsers don’t mind about a missing padding at the end of a base64 encoded data URL, this implementation will raise an ValueError in that case.

21.6.18. FTPHandler Objects ¶

FTPHandler. ftp_open ( req ) ¶

打开 FTP (文件传输协议) 文件指示通过 req 。登录始终使用空用户名和口令完成。

21.6.19. CacheFTPHandler Objects ¶

CacheFTPHandler 对象是 FTPHandler 对象，具有以下额外方法：

CacheFTPHandler. setTimeout ( t ) ¶

把连接超时设为 t 秒。

CacheFTPHandler. setMaxConns ( m ) ¶

把缓存的最大连接数设为 m .

21.6.20. UnknownHandler Objects ¶

UnknownHandler. unknown_open ( ) ¶

引发 URLError 异常。

21.6.21. HTTPErrorProcessor Objects ¶

HTTPErrorProcessor. http_response ( ) ¶

处理 HTTP 错误响应。

对于 200 错误代码，响应对象被立即返回。

For non-200 error codes, this simply passes the job on to the protocol_error_code() 处理程序方法，凭借 OpenerDirector.error() . Eventually, HTTPDefaultErrorHandler 将引发 HTTPError 若没有其它处理程序处理错误。

HTTPErrorProcessor. https_response ( ) ¶

处理 HTTPS 错误响应。

行为如同 http_response() .

21.6.22. Examples ¶

此范例获取 python.org 主页并显示其前 300 字节。

>>> import urllib.request
>>> with urllib.request.urlopen('http://www.python.org/') as f:
...     print(f.read(300))
...
b'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">\n\n\n<html
xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">\n\n<head>\n
<meta http-equiv="content-type" content="text/html; charset=utf-8" />\n
<title>Python Programming '
					

Note that urlopen returns a bytes object. This is because there is no way for urlopen to automatically determine the encoding of the byte stream it receives from the http server. In general, a program will decode the returned bytes object to string once it determines or guesses the appropriate encoding.

The following W3C document, http://www.w3.org/International/O-charset , lists the various ways in which a (X)HTML or a XML document could have specified its encoding information.

As the python.org website uses utf-8 encoding as specified in its meta tag, we will use the same for decoding the bytes object.

>>> with urllib.request.urlopen('http://www.python.org/') as f:
...     print(f.read(100).decode('utf-8'))
...
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtm
					

It is also possible to achieve the same result without using the 上下文管理器 approach.

>>> import urllib.request
>>> f = urllib.request.urlopen('http://www.python.org/')
>>> print(f.read(100).decode('utf-8'))
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtm
					

In the following example, we are sending a data-stream to the stdin of a CGI and reading the data it returns to us. Note that this example will only work when the Python installation supports SSL.

>>> import urllib.request
>>> req = urllib.request.Request(url='https://localhost/cgi-bin/test.cgi',
...                       data=b'This data is passed to stdin of the CGI')
>>> with urllib.request.urlopen(req) as f:
...     print(f.read().decode('utf-8'))
...
Got Data: "This data is passed to stdin of the CGI"
					

The code for the sample CGI used in the above example is:

#!/usr/bin/env python
import sys
data = sys.stdin.read()
print('Content-type: text/plain\n\nGot Data: "%s"' % data)
					

Here is an example of doing a PUT request using Request :

import urllib.request
DATA=b'some data'
req = urllib.request.Request(url='http://localhost:8080', data=DATA,method='PUT')
with urllib.request.urlopen(req) as f:
    pass
print(f.status)
print(f.reason)
					

Use of Basic HTTP Authentication:

import urllib.request
# Create an OpenerDirector with support for Basic HTTP Authentication...
auth_handler = urllib.request.HTTPBasicAuthHandler()
auth_handler.add_password(realm='PDQ Application',
                          uri='https://mahler:8092/site-updates.py',
                          user='klem',
                          passwd='kadidd!ehopper')
opener = urllib.request.build_opener(auth_handler)
# ...and install it globally so it can be used with urlopen.
urllib.request.install_opener(opener)
urllib.request.urlopen('http://www.example.com/login.html')
					

build_opener() provides many handlers by default, including a ProxyHandler 。默认情况下， ProxyHandler uses the environment variables named <scheme>_proxy ，其中 <scheme> is the URL scheme involved. For example, the http_proxy environment variable is read to obtain the HTTP proxy’s URL.

This example replaces the default ProxyHandler with one that uses programmatically-supplied proxy URLs, and adds proxy authorization support with ProxyBasicAuthHandler .

proxy_handler = urllib.request.ProxyHandler({'http': 'http://www.example.com:3128/'})
proxy_auth_handler = urllib.request.ProxyBasicAuthHandler()
proxy_auth_handler.add_password('realm', 'host', 'username', 'password')
opener = urllib.request.build_opener(proxy_handler, proxy_auth_handler)
# This time, rather than install the OpenerDirector, we use it directly:
opener.open('http://www.example.com/login.html')
					

添加 HTTP 头：

使用 headers 自变量到 Request 构造函数，或：

import urllib.request
req = urllib.request.Request('http://www.example.com/')
req.add_header('Referer', 'http://www.python.org/')
r = urllib.request.urlopen(req)
					

OpenerDirector 自动添加 User-Agent 头到每个 Request 。要改变这：

import urllib.request
opener = urllib.request.build_opener()
opener.addheaders = [('User-agent', 'Mozilla/5.0')]
opener.open('http://www.example.com/')
					

Also, remember that a few standard headers ( Content-Length , Content-Type and Host ) are added when the Request 被传递给 urlopen() (或 OpenerDirector.open() ).

这里是范例会话使用 GET 方法以检索 URL 包含参数：

>>> import urllib.request
>>> import urllib.parse
>>> params = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
>>> url = "http://www.musi-cal.com/cgi-bin/query?%s" % params
>>> with urllib.request.urlopen(url) as f:
...     print(f.read().decode('utf-8'))
...
					

以下范例使用 POST method instead. Note that params output from urlencode is encoded to bytes before it is sent to urlopen as data:

>>> import urllib.request
>>> import urllib.parse
>>> data = urllib.parse.urlencode({'spam': 1, 'eggs': 2, 'bacon': 0})
>>> data = data.encode('ascii')
>>> with urllib.request.urlopen("http://requestb.in/xrbl82xr", data) as f:
...     print(f.read().decode('utf-8'))
...
					

The following example uses an explicitly specified HTTP proxy, overriding environment settings:

>>> import urllib.request
>>> proxies = {'http': 'http://proxy.example.com:8080/'}
>>> opener = urllib.request.FancyURLopener(proxies)
>>> with opener.open("http://www.python.org") as f:
...     f.read().decode('utf-8')
...
					

以下范例根本不使用代理，覆盖环境设置：

>>> import urllib.request
>>> opener = urllib.request.FancyURLopener({})
>>> with opener.open("http://www.python.org/") as f:
...     f.read().decode('utf-8')
...
					

21.6.23. Legacy interface ¶

以下函数和类移植自 Python 2 模块 urllib (而不是 urllib2 )。未来某个时候可能弃用它们。

urllib.request. urlretrieve ( url , filename=None , reporthook=None , data=None ) ¶

Copy a network object denoted by a URL to a local file. If the URL points to a local file, the object will not be copied unless filename is supplied. 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). 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 hook function that will be called once on establishment of the network connection and once after each block read thereafter. The hook 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.

The following example illustrates the most common usage scenario:

>>> import urllib.request
>>> local_filename, headers = urllib.request.urlretrieve('http://python.org/')
>>> html = open(local_filename)
>>> html.close()
							

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 a bytes object in standard application/x-www-form-urlencoded 格式；见 urllib.parse.urlencode() 函数。

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.

urllib.request. urlcleanup ( ) ¶

Cleans up temporary files that may have been left behind by previous calls to urlretrieve() .

class urllib.request. URLopener ( proxies=None , **x509 ) ¶

从 3.3 版起弃用。

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.

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 OSError 异常若服务器返回错误代码。

open ( fullurl , data=None ) ¶

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=None ) ¶

能打开未知 URL 类型的可覆盖接口。

retrieve ( url , filename=None , reporthook=None , data=None ) ¶

Retrieves the contents of url and places it in filename . The return value is a tuple consisting of a local filename and either an email.message.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: A chunk number, the maximum size chunks are read in and the total size of the download (-1 if unknown). It will be called once at the start and 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 urllib.parse.urlencode() 函数。

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.

class urllib.request. FancyURLopener ( ... ) ¶

从 3.3 版起弃用。

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.

21.6.24. urllib.request 限定 ¶

• 目前，只支持以下协议：HTTP (第 0.9 和 1.0 版)、FTP、本地文件及数据 URL。

  3.4 版改变： 添加支持数据 URL。

• 缓存特征的 urlretrieve() 已被禁用，直到有人找到时间骇客 Expiration (过期) 时间头的适当处理。

• 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 html.parser 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。