"urllib.request" --- Extensible library for opening URLs
********************************************************

**Kod źródłowy:** Lib/urllib/request.py

======================================================================

The "urllib.request" module defines functions and classes which help
in opening URLs (mostly HTTP) in a complex world --- basic and digest
authentication, redirections, cookies and more.

Zobacz także:

  The Requests package is recommended for a higher-level HTTP client
  interface.

Ostrzeżenie:

  On macOS it is unsafe to use this module in programs using
  "os.fork()" because the "getproxies()" implementation for macOS uses
  a higher-level system API. Set the environment variable "no_proxy"
  to "*" to avoid this problem (e.g. "os.environ["no_proxy"] = "*"").

Dostępność: not WASI.

This module does not work or is not available on WebAssembly. See
WebAssembly platforms for more information.

The "urllib.request" module defines the following functions:

urllib.request.urlopen(url, data=None, [timeout, ]*, context=None)

   Open *url*, which can be either a string containing a valid,
   properly encoded URL, or a "Request" object.

   *data* must be an object specifying additional data to be sent to
   the server, or "None" if no such data is needed.  See "Request" for
   details.

   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.

   This function always returns an object which can work as a *context
   manager* and has the properties *url*, *headers*, and *status*. See
   "urllib.response.addinfourl" for more detail on these properties.

   For HTTP and HTTPS URLs, this function returns a
   "http.client.HTTPResponse" object slightly modified. In addition to
   the three new methods above, the msg attribute contains the same
   information as the "reason" attribute --- the reason phrase
   returned by server --- instead of the response headers as it is
   specified in the documentation for "HTTPResponse".

   For FTP, file, and data URLs, this function returns a
   "urllib.response.addinfourl" object.

   Raises "URLError" on protocol 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.

   The default opener raises an auditing event "urllib.Request" with
   arguments "fullurl", "data", "headers", "method" taken from the
   request object.

   Zmienione w wersji 3.2: *cafile* and *capath* were added.HTTPS
   virtual hosts are now supported if possible (that is, if
   "ssl.HAS_SNI" is true).*data* can be an iterable object.

   Zmienione w wersji 3.3: *cadefault* was added.

   Zmienione w wersji 3.4.3: *context* was added.

   Zmienione w wersji 3.10: HTTPS connection now send an ALPN
   extension with protocol indicator "http/1.1" when no *context* is
   given. Custom *context* should set ALPN protocols with
   "set_alpn_protocols()".

   Zmienione w wersji 3.13: Remove *cafile*, *capath* and *cadefault*
   parameters: use the *context* parameter instead.

urllib.request.install_opener(opener)

   Install an "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()" instead
   of "urlopen()".  The code does not check for a real
   "OpenerDirector", and any class with the appropriate interface will
   work.

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

   Return an "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".

   If the Python installation has SSL support (i.e., if the "ssl"
   module can be imported), "HTTPSHandler" will also be added.

   A "BaseHandler" subclass may also change its "handler_order"
   attribute to modify its position in the handlers list.

urllib.request.pathname2url(path, *, add_scheme=False)

   Convert the given local path to a "file:" URL. This function uses
   "quote()" function to encode the path.

   If *add_scheme* is false (the default), the return value omits the
   "file:" scheme prefix. Set *add_scheme* to true to return a
   complete URL.

   This example shows the function being used on Windows:

      >>> from urllib.request import pathname2url
      >>> path = 'C:\\Program Files'
      >>> pathname2url(path, add_scheme=True)
      'file:///C:/Program%20Files'

   Zmienione w wersji 3.14: Windows drive letters are no longer
   converted to uppercase, and ":" characters not following a drive
   letter no longer cause an "OSError" exception to be raised on
   Windows.

   Zmienione w wersji 3.14: Paths beginning with a slash are converted
   to URLs with authority sections. For example, the path "/etc/hosts"
   is converted to the URL "///etc/hosts".

   Zmienione w wersji 3.14: The *add_scheme* parameter was added.

urllib.request.url2pathname(url, *, require_scheme=False, resolve_host=False)

   Convert the given "file:" URL to a local path. This function uses
   "unquote()" to decode the URL.

   If *require_scheme* is false (the default), the given value should
   omit a "file:" scheme prefix. If *require_scheme* is set to true,
   the given value should include the prefix; a "URLError" is raised
   if it doesn't.

   The URL authority is discarded if it is empty, "localhost", or the
   local hostname. Otherwise, if *resolve_host* is set to true, the
   authority is resolved using "socket.gethostbyname()" and discarded
   if it matches a local IP address (as per **RFC 8089 §3**). If the
   authority is still unhandled, then on Windows a UNC path is
   returned, and on other platforms a "URLError" is raised.

   This example shows the function being used on Windows:

      >>> from urllib.request import url2pathname
      >>> url = 'file:///C:/Program%20Files'
      >>> url2pathname(url, require_scheme=True)
      'C:\\Program Files'

   Zmienione w wersji 3.14: Windows drive letters are no longer
   converted to uppercase, and ":" characters not following a drive
   letter no longer cause an "OSError" exception to be raised on
   Windows.

   Zmienione w wersji 3.14: The URL authority is discarded if it
   matches the local hostname. Otherwise, if the authority isn't empty
   or "localhost", then on Windows a UNC path is returned (as before),
   and on other platforms a "URLError" is raised.

   Zmienione w wersji 3.14: The URL query and fragment components are
   discarded if present.

   Zmienione w wersji 3.14: The *require_scheme* and *resolve_host*
   parameters were added.

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 System Configuration for macOS and Windows Systems
   Registry for Windows. If both lowercase and uppercase environment
   variables exist (and disagree), lowercase is preferred.

   Informacja:

     If the environment variable "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" suffix).

The following classes are provided:

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

   This class is an abstraction of a URL request.

   *url* should be a string containing a valid, properly encoded URL.

   *data* must be an object specifying additional data to send to the
   server, or "None" if no such data is needed.  Currently HTTP
   requests are the only ones that use *data*.  The supported object
   types include bytes, file-like objects, and iterables of bytes-like
   objects. If no "Content-Length" nor "Transfer-Encoding" header
   field has been provided, "HTTPHandler" will set these headers
   according to the type of *data*.  "Content-Length" will be used to
   send bytes objects, while "Transfer-Encoding: chunked" as specified
   in **RFC 7230**, Section 3.3.1 will be used to send files and other
   iterables.

   For an HTTP POST request method, *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 an ASCII string in this format. It should be
   encoded to bytes before being used as the *data* parameter.

   *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 value, 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"", while
   "urllib"'s default user agent string is ""Python-urllib/2.6"" (on
   Python 2.6). All header keys are sent in camel case.

   An appropriate "Content-Type" header should be included if the
   *data* argument is present.  If this header has not been provided
   and *data* is not "None", "Content-Type: application/x-www-form-
   urlencoded" will be added as a default.

   The next two arguments are only of interest for correct handling of
   third-party HTTP cookies:

   *origin_req_host* should be the request-host of the origin
   transaction, as defined by **RFC 2965**.  It defaults to
   "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.

   *method* should be a string that indicates the HTTP request method
   that will be used (e.g. "'HEAD'").  If provided, its value is
   stored in the "method" attribute and is used by "get_method()". The
   default is "'GET'" if *data* is "None" or "'POST'" otherwise.
   Subclasses may indicate a different default method by setting the
   "method" attribute in the class itself.

   Informacja:

     The request will not work as expected if the data object is
     unable to deliver its content more than once (e.g. a file or an
     iterable that can produce the content only once) and the request
     is retried for HTTP redirects or authentication.  The *data* is
     sent to the HTTP server right away after the headers.  There is
     no support for a 100-continue expectation in the library.

   Zmienione w wersji 3.3: "Request.method" argument is added to the
   Request class.

   Zmienione w wersji 3.4: Default "Request.method" may be indicated
   at the class level.

   Zmienione w wersji 3.6: Do not raise an error if the "Content-
   Length" has not been provided and *data* is neither "None" nor a
   bytes object. Fall back to use chunked transfer encoding instead.

class urllib.request.OpenerDirector

   The "OpenerDirector" class opens URLs via "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" exceptions.

class urllib.request.HTTPRedirectHandler

   A class to handle redirections.

class urllib.request.HTTPCookieProcessor(cookiejar=None)

   A class to handle HTTP Cookies.

class urllib.request.ProxyHandler(proxies=None)

   Cause requests to go through a proxy. If *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 macOS
   environment proxy information is retrieved from the System
   Configuration Framework.

   To disable autodetected proxy pass an empty dictionary.

   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".

   Informacja:

     "HTTP_PROXY" will be ignored if a variable "REQUEST_METHOD" is
     set; see the documentation on "getproxies()".

class urllib.request.HTTPPasswordMgr

   Keep a database of  "(realm, uri) -> (user, password)" mappings.

class urllib.request.HTTPPasswordMgrWithDefaultRealm

   Keep a database of  "(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.HTTPPasswordMgrWithPriorAuth

   A variant of "HTTPPasswordMgrWithDefaultRealm" that also has a
   database of "uri -> is_authenticated" mappings.  Can be used by a
   BasicAuth handler to determine when to send authentication
   credentials immediately instead of waiting for a "401" response
   first.

    Dodane w wersji 3.5.

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 Objects for information on the interface
   that must be supported.  If *passwd_mgr* also provides
   "is_authenticated" and "update_authenticated" methods (see
   HTTPPasswordMgrWithPriorAuth Objects), then the handler will use
   the "is_authenticated" result for a given URI to determine whether
   or not to send authentication credentials with the request.  If
   "is_authenticated" returns "True" for the URI, credentials are
   sent.  If "is_authenticated" is "False", credentials are not sent,
   and then if a "401" response is received the request is re-sent
   with the authentication credentials.  If authentication succeeds,
   "update_authenticated" is called to set "is_authenticated" "True"
   for the URI, so that subsequent requests to the URI or any of its
   super-URIs will automatically include the authentication
   credentials.

    Dodane w wersji 3.5: Added "is_authenticated" support.

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 Objects 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 Objects 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 Objects for information on the interface
   that must be supported.

   Zmienione w wersji 3.14: Added support for HTTP digest
   authentication algorithm "SHA-256".

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 Objects 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.

   Zmienione w wersji 3.3: Raise "ValueError" on unsupported
   Authentication Scheme.

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 Objects for information on the
   interface that must be supported.

class urllib.request.HTTPHandler

   A class to handle opening of HTTP URLs.

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

   A class to handle opening of HTTPS URLs.  *context* and
   *check_hostname* have the same meaning as in
   "http.client.HTTPSConnection".

   Zmienione w wersji 3.2: *context* and *check_hostname* were added.

class urllib.request.FileHandler

   Open local files.

class urllib.request.DataHandler

   Open data URLs.

    Dodane w wersji 3.4.

class urllib.request.FTPHandler

   Open FTP URLs.

class urllib.request.CacheFTPHandler

   Open FTP URLs, keeping a cache of open FTP connections to minimize
   delays.

class urllib.request.UnknownHandler

   A catch-all class to handle unknown URLs.

class urllib.request.HTTPErrorProcessor

   Process HTTP error responses.


Request Objects
===============

The following methods describe "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

   The original URL passed to the constructor.

   Zmienione w wersji 3.4.

   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

   The URI scheme.

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.selector

   The URI path.  If the "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.

   Zmienione w wersji 3.4: 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.method

   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 *method* argument.

    Dodane w wersji 3.3.

   Zmienione w wersji 3.4: 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" is not "None", return its value, otherwise return
   "'GET'" if "Request.data" is "None", or "'POST'" if it's not. This
   is only meaningful for HTTP requests.

   Zmienione w wersji 3.3: get_method now looks at the value of
   "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.  Note that headers
   added using this method are also added to redirected requests.

Request.add_unredirected_header(key, header)

   Add a header that will not be added to a redirected request.

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).

    Dodane w wersji 3.4.

Request.get_full_url()

   Return the URL given in the constructor.

   Zmienione w wersji 3.4.

   Returns "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.

Zmienione w wersji 3.4: 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.


OpenerDirector Objects
======================

"OpenerDirector" instances have the following methods:

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).  Note that, in the following,
   *protocol* should be replaced with the actual protocol to handle,
   for example "http_response()" would be the HTTP protocol response
   handler.  Also *type* should be replaced with the actual HTTP code,
   for example "http_error_404()" would handle HTTP 404 errors.

   * "<protocol>_open()" --- signal that the handler knows how to open
     *protocol* URLs.

     See "BaseHandler.<protocol>_open()" for more information.

   * "http_error_<type>()" --- signal that the handler knows how to
     handle HTTP errors with HTTP error code *type*.

     See "BaseHandler.http_error_<nnn>()" for more information.

   * "<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.

     See "BaseHandler.<protocol>_request()" for more information.

   * "<protocol>_response()" --- signal that the handler knows how to
     post-process *protocol* responses.

     See "BaseHandler.<protocol>_response()" for more information.

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

   Open the given *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_<type>()" methods
   of the handler classes.

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

OpenerDirector objects open URLs in three stages:

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()"
   methods.

3. Every handler with a method named like "<protocol>_response()" has
   that method called to post-process the response.


BaseHandler Objects
===================

"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()

   Remove any parents.

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

Informacja:

  The convention has been adopted that subclasses defining
  "<protocol>_request()" or "<protocol>_response()" methods are named
  "*Processor"; all others are named "*Handler".

BaseHandler.parent

   A valid "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()" method of "OpenerDirector", or
   "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.

   "OpenerDirector" will call this method with five positional
   arguments:

   1. a "Request" object,

   2. a file-like object with the HTTP error body,

   3. the three-digit code of the error, as a string,

   4. the user-visible explanation of the code, as a string, and

   5. the headers of the error, as a mapping object.

   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*
   occurs.

   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* will be a "Request" object. The return
   value should be a "Request" object.

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* will be a "Request" object. *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()".


HTTPRedirectHandler Objects
===========================

Informacja:

  Some HTTP redirections require action from this module's client
  code.  If this is the case, "HTTPError" is raised.  See **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)

   Return a "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.

   Informacja:

     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)

   Redirect to the "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)

   The same as "http_error_301()", but called for the 'found'
   response.

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

   The same as "http_error_301()", but called for the 'see other'
   response.

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

   The same as "http_error_301()", but called for the 'temporary
   redirect' response. It does not allow changing the request method
   from "POST" to "GET".

HTTPRedirectHandler.http_error_308(req, fp, code, msg, hdrs)

   The same as "http_error_301()", but called for the 'permanent
   redirect' response. It does not allow changing the request method
   from "POST" to "GET".

    Dodane w wersji 3.11.


HTTPCookieProcessor Objects
===========================

"HTTPCookieProcessor" instances have one attribute:

HTTPCookieProcessor.cookiejar

   The "http.cookiejar.CookieJar" in which cookies are stored.


ProxyHandler Objects
====================

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.


HTTPPasswordMgr Objects
=======================

These methods are available on "HTTPPasswordMgr" and
"HTTPPasswordMgrWithDefaultRealm" objects.

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" objects, the realm "None"
   will be searched if the given *realm* has no matching
   user/password.


HTTPPasswordMgrWithPriorAuth Objects
====================================

This password manager extends "HTTPPasswordMgrWithDefaultRealm" to
support tracking URIs for which authentication credentials should
always be sent.

HTTPPasswordMgrWithPriorAuth.add_password(realm, uri, user, passwd, is_authenticated=False)

   *realm*, *uri*, *user*, *passwd* are as for
   "HTTPPasswordMgr.add_password()".  *is_authenticated* sets the
   initial value of the "is_authenticated" flag for the given URI or
   list of URIs. If *is_authenticated* is specified as "True", *realm*
   is ignored.

HTTPPasswordMgrWithPriorAuth.find_user_password(realm, authuri)

   Same as for "HTTPPasswordMgrWithDefaultRealm" objects

HTTPPasswordMgrWithPriorAuth.update_authenticated(self, uri, is_authenticated=False)

   Update the "is_authenticated" flag for the given *uri* or list of
   URIs.

HTTPPasswordMgrWithPriorAuth.is_authenticated(self, authuri)

   Returns the current state of the "is_authenticated" flag for the
   given URI.


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).


HTTPBasicAuthHandler Objects
============================

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

   Retry the request with authentication information, if available.


ProxyBasicAuthHandler Objects
=============================

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

   Retry the request with authentication information, if available.


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.


HTTPDigestAuthHandler Objects
=============================

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

   Retry the request with authentication information, if available.


ProxyDigestAuthHandler Objects
==============================

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

   Retry the request with authentication information, if available.


HTTPHandler Objects
===================

HTTPHandler.http_open(req)

   Send an HTTP request, which can be either GET or POST, depending on
   "req.data".


HTTPSHandler Objects
====================

HTTPSHandler.https_open(req)

   Send an HTTPS request, which can be either GET or POST, depending
   on "req.data".


FileHandler Objects
===================

FileHandler.file_open(req)

   Open the file locally, if there is no host name, or the host name
   is "'localhost'".

   Zmienione w wersji 3.2: This method is applicable only for local
   hostnames.  When a remote hostname is given, a "URLError" is
   raised.


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 a "ValueError" in that case.


FTPHandler Objects
==================

FTPHandler.ftp_open(req)

   Open the FTP file indicated by *req*. The login is always done with
   empty username and password.


CacheFTPHandler Objects
=======================

"CacheFTPHandler" objects are "FTPHandler" objects with the following
additional methods:

CacheFTPHandler.setTimeout(t)

   Set timeout of connections to *t* seconds.

CacheFTPHandler.setMaxConns(m)

   Set maximum number of cached connections to *m*.


UnknownHandler Objects
======================

UnknownHandler.unknown_open()

   Raise a "URLError" exception.


HTTPErrorProcessor Objects
==========================

HTTPErrorProcessor.http_response(request, response)

   Process HTTP error responses.

   For 200 error codes, the response object is returned immediately.

   For non-200 error codes, this simply passes the job on to the
   "http_error_<type>()" handler methods, via
   "OpenerDirector.error()". Eventually, "HTTPDefaultErrorHandler"
   will raise an "HTTPError" if no other handler handles the error.

HTTPErrorProcessor.https_response(request, response)

   Process HTTPS error responses.

   The behavior is same as "http_response()".


Przykłady
=========

In addition to the examples below, more examples are given in HOWTO
Fetch Internet Resources Using The urllib Package.

This example gets the python.org main page and displays the first 300
bytes of it:

   >>> import urllib.request
   >>> with urllib.request.urlopen('http://www.python.org/') as f:
   ...     print(f.read(300))
   ...
   b'<!doctype html>\n<!--[if lt IE 7]>   <html class="no-js ie6 lt-ie7 lt-ie8 lt-ie9">   <![endif]-->\n<!--[if IE 7]>      <html class="no-js ie7 lt-ie8 lt-ie9">          <![endif]-->\n<!--[if IE 8]>      <html class="no-js ie8 lt-ie9">

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 HTML spec document,
https://html.spec.whatwg.org/#charset, lists the various ways in which
an HTML or an XML document could have specified its encoding
information.

For additional information, see the W3C document:
https://www.w3.org/International/questions/qa-html-encoding-
declarations.

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>
   <!--[if lt IE 7]>   <html class="no-js ie6 lt-ie7 lt-ie8 lt-ie9">   <![endif]-->
   <!-

It is also possible to achieve the same result without using the
*context manager* approach:

   >>> import urllib.request
   >>> f = urllib.request.urlopen('http://www.python.org/')
   >>> try:
   ...     print(f.read(100).decode('utf-8'))
   ... finally:
   ...     f.close()
   ...
   <!doctype html>
   <!--[if lt IE 7]>   <html class="no-js ie6 lt-ie7 lt-ie8 lt-ie9">   <![endif]-->
   <!--

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)
   with urllib.request.urlopen('http://www.example.com/login.html') as f:
       print(f.read().decode('utf-8'))

"build_opener()" provides many handlers by default, including a
"ProxyHandler".  By default, "ProxyHandler" uses the environment
variables named "<scheme>_proxy", where "<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:
   with opener.open('http://www.example.com/login.html') as f:
      print(f.read().decode('utf-8'))

Adding HTTP headers:

Use the *headers* argument to the "Request" constructor, or:

   import urllib.request
   req = urllib.request.Request('http://www.example.com/')
   req.add_header('Referer', 'http://www.python.org/')
   # Customize the default User-Agent header value:
   req.add_header('User-Agent', 'urllib-example/0.1 (Contact: . . .)')
   with urllib.request.urlopen(req) as f:
       print(f.read().decode('utf-8'))

"OpenerDirector" automatically adds a *User-Agent* header to every
"Request".  To change this:

   import urllib.request
   opener = urllib.request.build_opener()
   opener.addheaders = [('User-agent', 'Mozilla/5.0')]
   with opener.open('http://www.example.com/') as f:
      print(f.read().decode('utf-8'))

Also, remember that a few standard headers (*Content-Length*,
*Content-Type* and *Host*) are added when the "Request" is passed to
"urlopen()" (or "OpenerDirector.open()").

Here is an example session that uses the "GET" method to retrieve a
URL containing parameters:

   >>> 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'))
   ...

The following example uses the "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.build_opener(urllib.request.ProxyHandler(proxies))
   >>> with opener.open("http://www.python.org") as f:
   ...     f.read().decode('utf-8')
   ...

The following example uses no proxies at all, overriding environment
settings:

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


Legacy interface
================

The following functions and classes are ported from the Python 2
module "urllib" (as opposed to "urllib2").  They might become
deprecated at some point in the future.

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 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.

   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()

   If the *url* uses the "http:" scheme identifier, the optional
   *data* argument may be given to specify a "POST" request (normally
   the request type is "GET").  The *data* argument must be a bytes
   object in standard *application/x-www-form-urlencoded* format; see
   the "urllib.parse.urlencode()" function.

   "urlretrieve()" will raise "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.

   If no *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()".


"urllib.request" Restrictions
=============================

* Currently, only the following protocols are supported: HTTP
  (versions 0.9 and 1.0), FTP, local files, and data URLs.

  Zmienione w wersji 3.4: Added support for data URLs.

* The caching feature of "urlretrieve()" has been disabled until
  someone finds the time to hack proper processing of Expiration time
  headers.

* There should be a function to query whether a particular URL is in
  the cache.

* 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.

* The data returned by "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* header.  If the returned data is HTML, you can
  use the module "html.parser" to parse it.

* 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" module.


"urllib.response" --- Response classes used by urllib
*****************************************************

The "urllib.response" module defines functions and classes which
define a minimal file-like interface, including "read()" and
"readline()". Functions defined by this module are used internally by
the "urllib.request" module. The typical response object is a
"urllib.response.addinfourl" instance:

class urllib.response.addinfourl

   url

      URL of the resource retrieved, commonly used to determine if a
      redirect was followed.

   headers

      Returns the headers of the response in the form of an
      "EmailMessage" instance.

   status

       Dodane w wersji 3.9.

      Status code returned by server.

   geturl()

      Niezalecane od wersji 3.9: Deprecated in favor of "url".

   info()

      Niezalecane od wersji 3.9: Deprecated in favor of "headers".

   code

      Niezalecane od wersji 3.9: Deprecated in favor of "status".

   getcode()

      Niezalecane od wersji 3.9: Deprecated in favor of "status".
