\section{\module{urllib2} --- extensible library for opening URLs} \declaremodule{standard}{urllib2}\moduleauthor{Jeremy Hylton}{jhylton@users.sourceforge.net}\sectionauthor{Moshe Zadka}{moshez@users.sourceforge.net} \modulesynopsis{An extensible library for opening URLs using a variety of protocols} The \module{urllib2} module defines functions and classes which helpin opening URLs (mostly HTTP) in a complex world --- basic and digestauthentication, redirections, cookies and more. The \module{urllib2} module defines the following functions: \begin{funcdesc}{urlopen}{url\optional{, data}}Open the URL \var{url}, which can be either a string or a \class{Request}object. \var{data} may be a string specifying additional data to send to theserver, or \code{None} if no such data is needed. Currently HTTP requests are the only ones that use \var{data};the HTTP request will be a POST instead of a GET when the \var{data}parameter is provided. \var{data} should be a buffer in the standard\mimetype{application/x-www-form-urlencoded} format. The\function{urllib.urlencode()} function takes a mapping or sequence of2-tuples and returns a string in this format. This function returns a file-like object with two additional methods: \begin{itemize} \item \method{geturl()} --- return the URL of the resource retrieved \item \method{info()} --- return the meta-information of the page, as a dictionary-like object\end{itemize} Raises \exception{URLError} on errors. Note that \code{None} may be returned if no handler handles therequest (though the default installed global \class{OpenerDirector}uses \class{UnknownHandler} to ensure this never happens).\end{funcdesc} \begin{funcdesc}{install_opener}{opener}Install an \class{OpenerDirector} instance as the default globalopener. Installing an opener is only necessary if you want urlopen touse that opener; otherwise, simply call \method{OpenerDirector.open()}instead of \function{urlopen()}. The code does not check for a real\class{OpenerDirector}, and any class with the appropriate interfacewill work.\end{funcdesc} \begin{funcdesc}{build_opener}{\optional{handler, \moreargs}}Return an \class{OpenerDirector} instance, which chains thehandlers in the order given. \var{handler}s can be either instancesof \class{BaseHandler}, or subclasses of \class{BaseHandler} (inwhich case it must be possible to call the constructor withoutany parameters). Instances of the following classes will be infront of the \var{handler}s, unless the \var{handler}s containthem, instances of them or subclasses of them:\class{ProxyHandler}, \class{UnknownHandler}, \class{HTTPHandler},\class{HTTPDefaultErrorHandler}, \class{HTTPRedirectHandler},\class{FTPHandler}, \class{FileHandler}, \class{HTTPErrorProcessor}. If the Python installation has SSL support (\function{socket.ssl()}exists), \class{HTTPSHandler} will also be added. Beginning in Python 2.3, a \class{BaseHandler} subclass may alsochange its \member{handler_order} member variable to modify itsposition in the handlers list.\end{funcdesc} The following exceptions are raised as appropriate: \begin{excdesc}{URLError}The handlers raise this exception (or derived exceptions) when theyrun into a problem. It is a subclass of \exception{IOError}.\end{excdesc} \begin{excdesc}{HTTPError}A subclass of \exception{URLError}, it can also function as a non-exceptional file-like return value (the same thing that\function{urlopen()} returns). This is useful when handling exoticHTTP errors, such as requests for authentication.\end{excdesc} \begin{excdesc}{GopherError}A subclass of \exception{URLError}, this is the error raised by theGopher handler.\end{excdesc} The following classes are provided: \begin{classdesc}{Request}{url\optional{, data}\optional{, headers} \optional{, origin_req_host}\optional{, unverifiable}}This class is an abstraction of a URL request. \var{url} should be a string containing a valid URL. \var{data} may be a string specifying additional data to send to theserver, or \code{None} if no such data is needed. Currently HTTP requests are the only ones that use \var{data};the HTTP request will be a POST instead of a GET when the \var{data}parameter is provided. \var{data} should be a buffer in the standard\mimetype{application/x-www-form-urlencoded} format. The\function{urllib.urlencode()} function takes a mapping or sequence of2-tuples and returns a string in this format. \var{headers} should be a dictionary, and will be treated as if\method{add_header()} was called with each key and value as arguments. The final two arguments are only of interest for correct handling ofthird-party HTTP cookies: \var{origin_req_host} should be the request-host of the origintransaction, as defined by \rfc{2965}. It defaults to\code{cookielib.request_host(self)}. This is the host name or IPaddress of the original request that was initiated by the user. Forexample, if the request is for an image in an HTML document, thisshould be the request-host of the request for the page containing theimage. \var{unverifiable} should indicate whether the request isunverifiable, as defined by RFC 2965. It defaults to False. Anunverifiable request is one whose URL the user did not have the optionto approve. For example, if the request is for an image in an HTMLdocument, and the user had no option to approve the automatic fetchingof the image, this should be true.\end{classdesc} \begin{classdesc}{OpenerDirector}{}The \class{OpenerDirector} class opens URLs via \class{BaseHandler}schained together. It manages the chaining of handlers, and recoveryfrom errors.\end{classdesc} \begin{classdesc}{BaseHandler}{}This is the base class for all registered handlers --- and handles onlythe simple mechanics of registration.\end{classdesc} \begin{classdesc}{HTTPDefaultErrorHandler}{}A class which defines a default handler for HTTP error responses; allresponses are turned into \exception{HTTPError} exceptions.\end{classdesc} \begin{classdesc}{HTTPRedirectHandler}{}A class to handle redirections.\end{classdesc} \begin{classdesc}{HTTPCookieProcessor}{\optional{cookiejar}}A class to handle HTTP Cookies.\end{classdesc} \begin{classdesc}{ProxyHandler}{\optional{proxies}}Cause requests to go through a proxy.If \var{proxies} is given, it must be a dictionary mappingprotocol names to URLs of proxies.The default is to read the list of proxies from the environmentvariables \envvar{<protocol>_proxy}.\end{classdesc} \begin{classdesc}{HTTPPasswordMgr}{}Keep a database of \code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})}mappings.\end{classdesc} \begin{classdesc}{HTTPPasswordMgrWithDefaultRealm}{}Keep a database of \code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})} mappings.A realm of \code{None} is considered a catch-all realm, which is searchedif no other realm fits.\end{classdesc} \begin{classdesc}{AbstractBasicAuthHandler}{\optional{password_mgr}}This is a mixin class that helps with HTTP authentication, bothto the remote host and to a proxy.\var{password_mgr}, if given, should be something that is compatiblewith \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr}for information on the interface that must be supported.\end{classdesc} \begin{classdesc}{HTTPBasicAuthHandler}{\optional{password_mgr}}Handle authentication with the remote host.\var{password_mgr}, if given, should be something that is compatiblewith \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr}for information on the interface that must be supported.\end{classdesc} \begin{classdesc}{ProxyBasicAuthHandler}{\optional{password_mgr}}Handle authentication with the proxy.\var{password_mgr}, if given, should be something that is compatiblewith \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr}for information on the interface that must be supported.\end{classdesc} \begin{classdesc}{AbstractDigestAuthHandler}{\optional{password_mgr}}This is a mixin class that helps with HTTP authentication, bothto the remote host and to a proxy.\var{password_mgr}, if given, should be something that is compatiblewith \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr}for information on the interface that must be supported.\end{classdesc} \begin{classdesc}{HTTPDigestAuthHandler}{\optional{password_mgr}}Handle authentication with the remote host.\var{password_mgr}, if given, should be something that is compatiblewith \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr}for information on the interface that must be supported.\end{classdesc} \begin{classdesc}{ProxyDigestAuthHandler}{\optional{password_mgr}}Handle authentication with the proxy.\var{password_mgr}, if given, should be something that is compatiblewith \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr}for information on the interface that must be supported.\end{classdesc} \begin{classdesc}{HTTPHandler}{}A class to handle opening of HTTP URLs.\end{classdesc} \begin{classdesc}{HTTPSHandler}{}A class to handle opening of HTTPS URLs.\end{classdesc} \begin{classdesc}{FileHandler}{}Open local files.\end{classdesc} \begin{classdesc}{FTPHandler}{}Open FTP URLs.\end{classdesc} \begin{classdesc}{CacheFTPHandler}{}Open FTP URLs, keeping a cache of open FTP connections to minimizedelays.\end{classdesc} \begin{classdesc}{GopherHandler}{}Open gopher URLs.\end{classdesc} \begin{classdesc}{UnknownHandler}{}A catch-all class to handle unknown URLs.\end{classdesc} \subsection{Request Objects \label{request-objects}} The following methods describe all of \class{Request}'s public interface,and so all must be overridden in subclasses. \begin{methoddesc}[Request]{add_data}{data}Set the \class{Request} data to \var{data}. This is ignored by allhandlers except HTTP handlers --- and there it should be a bytestring, and will change the request to be \code{POST} rather than\code{GET}.\end{methoddesc} \begin{methoddesc}[Request]{get_method}{}Return a string indicating the HTTP request method. This is onlymeaningful for HTTP requests, and currently always returns\code{'GET'} or \code{'POST'}.\end{methoddesc} \begin{methoddesc}[Request]{has_data}{}Return whether the instance has a non-\code{None} data.\end{methoddesc} \begin{methoddesc}[Request]{get_data}{}Return the instance's data.\end{methoddesc} \begin{methoddesc}[Request]{add_header}{key, val}Add another header to the request. Headers are currently ignored byall handlers except HTTP handlers, where they are added to the listof headers sent to the server. Note that there cannot be more thanone header with the same name, and later calls will overwriteprevious calls in case the \var{key} collides. Currently, this isno loss of HTTP functionality, since all headers which have meaningwhen used more than once have a (header-specific) way of gaining thesame functionality using only one header.\end{methoddesc} \begin{methoddesc}[Request]{add_unredirected_header}{key, header}Add a header that will not be added to a redirected request.\versionadded{2.4}\end{methoddesc} \begin{methoddesc}[Request]{has_header}{header}Return whether the instance has the named header (checks both regularand unredirected).\versionadded{2.4}\end{methoddesc} \begin{methoddesc}[Request]{get_full_url}{}Return the URL given in the constructor.\end{methoddesc} \begin{methoddesc}[Request]{get_type}{}Return the type of the URL --- also known as the scheme.\end{methoddesc} \begin{methoddesc}[Request]{get_host}{}Return the host to which a connection will be made.\end{methoddesc} \begin{methoddesc}[Request]{get_selector}{}Return the selector --- the part of the URL that is sent tothe server.\end{methoddesc} \begin{methoddesc}[Request]{set_proxy}{host, type}Prepare the request by connecting to a proxy server. The \var{host}and \var{type} will replace those of the instance, and the instance'sselector will be the original URL given in the constructor.\end{methoddesc} \begin{methoddesc}[Request]{get_origin_req_host}{}Return the request-host of the origin transaction, as defined by\rfc{2965}. See the documentation for the \class{Request}constructor.\end{methoddesc} \begin{methoddesc}[Request]{is_unverifiable}{}Return whether the request is unverifiable, as defined by RFC 2965.See the documentation for the \class{Request} constructor.\end{methoddesc} \subsection{OpenerDirector Objects \label{opener-director-objects}} \class{OpenerDirector} instances have the following methods: \begin{methoddesc}[OpenerDirector]{add_handler}{handler}\var{handler} should be an instance of \class{BaseHandler}. Thefollowing methods are searched, and added to the possible chains (notethat HTTP errors are a special case). \begin{itemize} \item \method{\var{protocol}_open()} --- signal that the handler knows how to open \var{protocol} URLs. \item \method{http_error_\var{type}()} --- signal that the handler knows how to handle HTTP errors with HTTP error code \var{type}. \item \method{\var{protocol}_error()} --- signal that the handler knows how to handle errors from (non-\code{http}) \var{protocol}. \item \method{\var{protocol}_request()} --- signal that the handler knows how to pre-process \var{protocol} requests. \item \method{\var{protocol}_response()} --- signal that the handler knows how to post-process \var{protocol} responses.\end{itemize}\end{methoddesc} \begin{methoddesc}[OpenerDirector]{open}{url\optional{, data}}Open the given \var{url} (which can be a request object or a string),optionally passing the given \var{data}.Arguments, return values and exceptions raised are the same as thoseof \function{urlopen()} (which simply calls the \method{open()} methodon the currently installed global \class{OpenerDirector}).\end{methoddesc} \begin{methoddesc}[OpenerDirector]{error}{proto\optional{, arg\optional{, \moreargs}}}Handle an error of the given protocol. This will call the registerederror handlers for the given protocol with the given arguments (whichare protocol specific). The HTTP protocol is a special case whichuses the HTTP response code to determine the specific error handler;refer to the \method{http_error_*()} methods of the handler classes. Return values and exceptions raised are the same as thoseof \function{urlopen()}.\end{methoddesc} OpenerDirector objects open URLs in three stages: The order in which these methods are called within each stage isdetermined by sorting the handler instances. \begin{enumerate} \item Every handler with a method named like \method{\var{protocol}_request()} has that method called to pre-process the request. \item Handlers with a method named like \method{\var{protocol}_open()} are called to handle the request. This stage ends when a handler either returns a non-\constant{None} value (ie. a response), or raises an exception (usually \exception{URLError}). Exceptions are allowed to propagate. In fact, the above algorithm is first tried for methods named \method{default_open}. If all such methods return \constant{None}, the algorithm is repeated for methods named like \method{\var{protocol}_open()}. If all such methods return \constant{None}, the algorithm is repeated for methods named \method{unknown_open()}. Note that the implementation of these methods may involve calls of the parent \class{OpenerDirector} instance's \method{.open()} and \method{.error()} methods. \item Every handler with a method named like \method{\var{protocol}_response()} has that method called to post-process the response. \end{enumerate} \subsection{BaseHandler Objects \label{base-handler-objects}} \class{BaseHandler} objects provide a couple of methods that aredirectly useful, and others that are meant to be used by derivedclasses. These are intended for direct use: \begin{methoddesc}[BaseHandler]{add_parent}{director}Add a director as parent.\end{methoddesc} \begin{methoddesc}[BaseHandler]{close}{}Remove any parents.\end{methoddesc} The following members and methods should only be used by classesderived from \class{BaseHandler}. \note{The convention has beenadopted that subclasses defining \method{\var{protocol}_request()} or\method{\var{protocol}_response()} methods are named\class{*Processor}; all others are named \class{*Handler}.} \begin{memberdesc}[BaseHandler]{parent}A valid \class{OpenerDirector}, which can be used to open using adifferent protocol, or handle errors.\end{memberdesc} \begin{methoddesc}[BaseHandler]{default_open}{req}This method is \emph{not} defined in \class{BaseHandler}, butsubclasses should define it if they want to catch all URLs. This method, if implemented, will be called by the parent\class{OpenerDirector}. It should return a file-like object asdescribed in the return value of the \method{open()} of\class{OpenerDirector}, or \code{None}. It should raise\exception{URLError}, unless a truly exceptional thing happens (forexample, \exception{MemoryError} should not be mapped to\exception{URLError}). This method will be called before any protocol-specific open method.\end{methoddesc} \begin{methoddescni}[BaseHandler]{\var{protocol}_open}{req}This method is \emph{not} defined in \class{BaseHandler}, butsubclasses should define it if they want to handle URLs with the givenprotocol. This method, if defined, will be called by the parent\class{OpenerDirector}. Return values should be the same as for \method{default_open()}.\end{methoddescni} \begin{methoddesc}[BaseHandler]{unknown_open}{req}This method is \var{not} defined in \class{BaseHandler}, butsubclasses should define it if they want to catch all URLs with nospecific registered handler to open it. This method, if implemented, will be called by the \member{parent} \class{OpenerDirector}. Return values should be the same as for \method{default_open()}.\end{methoddesc} \begin{methoddesc}[BaseHandler]{http_error_default}{req, fp, code, msg, hdrs}This method is \emph{not} defined in \class{BaseHandler}, butsubclasses should override it if they intend to provide a catch-allfor otherwise unhandled HTTP errors. It will be called automaticallyby the \class{OpenerDirector} getting the error, and should notnormally be called in other circumstances. \var{req} will be a \class{Request} object, \var{fp} will be afile-like object with the HTTP error body, \var{code} will be thethree-digit code of the error, \var{msg} will be the user-visibleexplanation of the code and \var{hdrs} will be a mapping object withthe headers of the error. Return values and exceptions raised should be the same as thoseof \function{urlopen()}.\end{methoddesc} \begin{methoddesc}[BaseHandler]{http_error_\var{nnn}}{req, fp, code, msg, hdrs}\var{nnn} should be a three-digit HTTP error code. This method isalso not defined in \class{BaseHandler}, but will be called, if itexists, on an instance of a subclass, when an HTTP error with code\var{nnn} occurs. Subclasses should override this method to handle specific HTTPLines 1–500 of 872. Load more
\section{\module{urllib2} --- extensible library for opening URLs} \declaremodule{standard}{urllib2} \moduleauthor{Jeremy Hylton}{jhylton@users.sourceforge.net} \sectionauthor{Moshe Zadka}{moshez@users.sourceforge.net} \modulesynopsis{An extensible library for opening URLs using a variety of protocols} The \module{urllib2} module defines functions and classes which help in opening URLs (mostly HTTP) in a complex world --- basic and digest authentication, redirections, cookies and more. The \module{urllib2} module defines the following functions: \begin{funcdesc}{urlopen}{url\optional{, data}} Open the URL \var{url}, which can be either a string or a \class{Request} object. \var{data} may be a string specifying additional data to send to the server, or \code{None} if no such data is needed. Currently HTTP requests are the only ones that use \var{data}; the HTTP request will be a POST instead of a GET when the \var{data} parameter is provided. \var{data} should be a buffer in the standard \mimetype{application/x-www-form-urlencoded} format. The \function{urllib.urlencode()} function takes a mapping or sequence of 2-tuples and returns a string in this format. This function returns a file-like object with two additional methods: \begin{itemize} \item \method{geturl()} --- return the URL of the resource retrieved \item \method{info()} --- return the meta-information of the page, as a dictionary-like object \end{itemize} Raises \exception{URLError} on errors. Note that \code{None} may be returned if no handler handles the request (though the default installed global \class{OpenerDirector} uses \class{UnknownHandler} to ensure this never happens). \end{funcdesc} \begin{funcdesc}{install_opener}{opener} Install an \class{OpenerDirector} instance as the default global opener. Installing an opener is only necessary if you want urlopen to use that opener; otherwise, simply call \method{OpenerDirector.open()} instead of \function{urlopen()}. The code does not check for a real \class{OpenerDirector}, and any class with the appropriate interface will work. \end{funcdesc} \begin{funcdesc}{build_opener}{\optional{handler, \moreargs}} Return an \class{OpenerDirector} instance, which chains the handlers in the order given. \var{handler}s can be either instances of \class{BaseHandler}, or subclasses of \class{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 \var{handler}s, unless the \var{handler}s contain them, instances of them or subclasses of them: \class{ProxyHandler}, \class{UnknownHandler}, \class{HTTPHandler}, \class{HTTPDefaultErrorHandler}, \class{HTTPRedirectHandler}, \class{FTPHandler}, \class{FileHandler}, \class{HTTPErrorProcessor}. If the Python installation has SSL support (\function{socket.ssl()} exists), \class{HTTPSHandler} will also be added. Beginning in Python 2.3, a \class{BaseHandler} subclass may also change its \member{handler_order} member variable to modify its position in the handlers list. \end{funcdesc} The following exceptions are raised as appropriate: \begin{excdesc}{URLError} The handlers raise this exception (or derived exceptions) when they run into a problem. It is a subclass of \exception{IOError}. \end{excdesc} \begin{excdesc}{HTTPError} A subclass of \exception{URLError}, it can also function as a non-exceptional file-like return value (the same thing that \function{urlopen()} returns). This is useful when handling exotic HTTP errors, such as requests for authentication. \end{excdesc} \begin{excdesc}{GopherError} A subclass of \exception{URLError}, this is the error raised by the Gopher handler. \end{excdesc} The following classes are provided: \begin{classdesc}{Request}{url\optional{, data}\optional{, headers} \optional{, origin_req_host}\optional{, unverifiable}} This class is an abstraction of a URL request. \var{url} should be a string containing a valid URL. \var{data} may be a string specifying additional data to send to the server, or \code{None} if no such data is needed. Currently HTTP requests are the only ones that use \var{data}; the HTTP request will be a POST instead of a GET when the \var{data} parameter is provided. \var{data} should be a buffer in the standard \mimetype{application/x-www-form-urlencoded} format. The \function{urllib.urlencode()} function takes a mapping or sequence of 2-tuples and returns a string in this format. \var{headers} should be a dictionary, and will be treated as if \method{add_header()} was called with each key and value as arguments. The final two arguments are only of interest for correct handling of third-party HTTP cookies: \var{origin_req_host} should be the request-host of the origin transaction, as defined by \rfc{2965}. It defaults to \code{cookielib.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. \var{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. \end{classdesc} \begin{classdesc}{OpenerDirector}{} The \class{OpenerDirector} class opens URLs via \class{BaseHandler}s chained together. It manages the chaining of handlers, and recovery from errors. \end{classdesc} \begin{classdesc}{BaseHandler}{} This is the base class for all registered handlers --- and handles only the simple mechanics of registration. \end{classdesc} \begin{classdesc}{HTTPDefaultErrorHandler}{} A class which defines a default handler for HTTP error responses; all responses are turned into \exception{HTTPError} exceptions. \end{classdesc} \begin{classdesc}{HTTPRedirectHandler}{} A class to handle redirections. \end{classdesc} \begin{classdesc}{HTTPCookieProcessor}{\optional{cookiejar}} A class to handle HTTP Cookies. \end{classdesc} \begin{classdesc}{ProxyHandler}{\optional{proxies}} Cause requests to go through a proxy. If \var{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 \envvar{<protocol>_proxy}. \end{classdesc} \begin{classdesc}{HTTPPasswordMgr}{} Keep a database of \code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})} mappings. \end{classdesc} \begin{classdesc}{HTTPPasswordMgrWithDefaultRealm}{} Keep a database of \code{(\var{realm}, \var{uri}) -> (\var{user}, \var{password})} mappings. A realm of \code{None} is considered a catch-all realm, which is searched if no other realm fits. \end{classdesc} \begin{classdesc}{AbstractBasicAuthHandler}{\optional{password_mgr}} This is a mixin class that helps with HTTP authentication, both to the remote host and to a proxy. \var{password_mgr}, if given, should be something that is compatible with \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr} for information on the interface that must be supported. \end{classdesc} \begin{classdesc}{HTTPBasicAuthHandler}{\optional{password_mgr}} Handle authentication with the remote host. \var{password_mgr}, if given, should be something that is compatible with \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr} for information on the interface that must be supported. \end{classdesc} \begin{classdesc}{ProxyBasicAuthHandler}{\optional{password_mgr}} Handle authentication with the proxy. \var{password_mgr}, if given, should be something that is compatible with \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr} for information on the interface that must be supported. \end{classdesc} \begin{classdesc}{AbstractDigestAuthHandler}{\optional{password_mgr}} This is a mixin class that helps with HTTP authentication, both to the remote host and to a proxy. \var{password_mgr}, if given, should be something that is compatible with \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr} for information on the interface that must be supported. \end{classdesc} \begin{classdesc}{HTTPDigestAuthHandler}{\optional{password_mgr}} Handle authentication with the remote host. \var{password_mgr}, if given, should be something that is compatible with \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr} for information on the interface that must be supported. \end{classdesc} \begin{classdesc}{ProxyDigestAuthHandler}{\optional{password_mgr}} Handle authentication with the proxy. \var{password_mgr}, if given, should be something that is compatible with \class{HTTPPasswordMgr}; refer to section~\ref{http-password-mgr} for information on the interface that must be supported. \end{classdesc} \begin{classdesc}{HTTPHandler}{} A class to handle opening of HTTP URLs. \end{classdesc} \begin{classdesc}{HTTPSHandler}{} A class to handle opening of HTTPS URLs. \end{classdesc} \begin{classdesc}{FileHandler}{} Open local files. \end{classdesc} \begin{classdesc}{FTPHandler}{} Open FTP URLs. \end{classdesc} \begin{classdesc}{CacheFTPHandler}{} Open FTP URLs, keeping a cache of open FTP connections to minimize delays. \end{classdesc} \begin{classdesc}{GopherHandler}{} Open gopher URLs. \end{classdesc} \begin{classdesc}{UnknownHandler}{} A catch-all class to handle unknown URLs. \end{classdesc} \subsection{Request Objects \label{request-objects}} The following methods describe all of \class{Request}'s public interface, and so all must be overridden in subclasses. \begin{methoddesc}[Request]{add_data}{data} Set the \class{Request} data to \var{data}. This is ignored by all handlers except HTTP handlers --- and there it should be a byte string, and will change the request to be \code{POST} rather than \code{GET}. \end{methoddesc} \begin{methoddesc}[Request]{get_method}{} Return a string indicating the HTTP request method. This is only meaningful for HTTP requests, and currently always returns \code{'GET'} or \code{'POST'}. \end{methoddesc} \begin{methoddesc}[Request]{has_data}{} Return whether the instance has a non-\code{None} data. \end{methoddesc} \begin{methoddesc}[Request]{get_data}{} Return the instance's data. \end{methoddesc} \begin{methoddesc}[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 \var{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. \end{methoddesc} \begin{methoddesc}[Request]{add_unredirected_header}{key, header} Add a header that will not be added to a redirected request. \versionadded{2.4} \end{methoddesc} \begin{methoddesc}[Request]{has_header}{header} Return whether the instance has the named header (checks both regular and unredirected). \versionadded{2.4} \end{methoddesc} \begin{methoddesc}[Request]{get_full_url}{} Return the URL given in the constructor. \end{methoddesc} \begin{methoddesc}[Request]{get_type}{} Return the type of the URL --- also known as the scheme. \end{methoddesc} \begin{methoddesc}[Request]{get_host}{} Return the host to which a connection will be made. \end{methoddesc} \begin{methoddesc}[Request]{get_selector}{} Return the selector --- the part of the URL that is sent to the server. \end{methoddesc} \begin{methoddesc}[Request]{set_proxy}{host, type} Prepare the request by connecting to a proxy server. The \var{host} and \var{type} will replace those of the instance, and the instance's selector will be the original URL given in the constructor. \end{methoddesc} \begin{methoddesc}[Request]{get_origin_req_host}{} Return the request-host of the origin transaction, as defined by \rfc{2965}. See the documentation for the \class{Request} constructor. \end{methoddesc} \begin{methoddesc}[Request]{is_unverifiable}{} Return whether the request is unverifiable, as defined by RFC 2965. See the documentation for the \class{Request} constructor. \end{methoddesc} \subsection{OpenerDirector Objects \label{opener-director-objects}} \class{OpenerDirector} instances have the following methods: \begin{methoddesc}[OpenerDirector]{add_handler}{handler} \var{handler} should be an instance of \class{BaseHandler}. The following methods are searched, and added to the possible chains (note that HTTP errors are a special case). \begin{itemize} \item \method{\var{protocol}_open()} --- signal that the handler knows how to open \var{protocol} URLs. \item \method{http_error_\var{type}()} --- signal that the handler knows how to handle HTTP errors with HTTP error code \var{type}. \item \method{\var{protocol}_error()} --- signal that the handler knows how to handle errors from (non-\code{http}) \var{protocol}. \item \method{\var{protocol}_request()} --- signal that the handler knows how to pre-process \var{protocol} requests. \item \method{\var{protocol}_response()} --- signal that the handler knows how to post-process \var{protocol} responses. \end{itemize} \end{methoddesc} \begin{methoddesc}[OpenerDirector]{open}{url\optional{, data}} Open the given \var{url} (which can be a request object or a string), optionally passing the given \var{data}. Arguments, return values and exceptions raised are the same as those of \function{urlopen()} (which simply calls the \method{open()} method on the currently installed global \class{OpenerDirector}). \end{methoddesc} \begin{methoddesc}[OpenerDirector]{error}{proto\optional{, arg\optional{, \moreargs}}} 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 \method{http_error_*()} methods of the handler classes. Return values and exceptions raised are the same as those of \function{urlopen()}. \end{methoddesc} 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. \begin{enumerate} \item Every handler with a method named like \method{\var{protocol}_request()} has that method called to pre-process the request. \item Handlers with a method named like \method{\var{protocol}_open()} are called to handle the request. This stage ends when a handler either returns a non-\constant{None} value (ie. a response), or raises an exception (usually \exception{URLError}). Exceptions are allowed to propagate. In fact, the above algorithm is first tried for methods named \method{default_open}. If all such methods return \constant{None}, the algorithm is repeated for methods named like \method{\var{protocol}_open()}. If all such methods return \constant{None}, the algorithm is repeated for methods named \method{unknown_open()}. Note that the implementation of these methods may involve calls of the parent \class{OpenerDirector} instance's \method{.open()} and \method{.error()} methods. \item Every handler with a method named like \method{\var{protocol}_response()} has that method called to post-process the response. \end{enumerate} \subsection{BaseHandler Objects \label{base-handler-objects}} \class{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: \begin{methoddesc}[BaseHandler]{add_parent}{director} Add a director as parent. \end{methoddesc} \begin{methoddesc}[BaseHandler]{close}{} Remove any parents. \end{methoddesc} The following members and methods should only be used by classes derived from \class{BaseHandler}. \note{The convention has been adopted that subclasses defining \method{\var{protocol}_request()} or \method{\var{protocol}_response()} methods are named \class{*Processor}; all others are named \class{*Handler}.} \begin{memberdesc}[BaseHandler]{parent} A valid \class{OpenerDirector}, which can be used to open using a different protocol, or handle errors. \end{memberdesc} \begin{methoddesc}[BaseHandler]{default_open}{req} This method is \emph{not} defined in \class{BaseHandler}, but subclasses should define it if they want to catch all URLs. This method, if implemented, will be called by the parent \class{OpenerDirector}. It should return a file-like object as described in the return value of the \method{open()} of \class{OpenerDirector}, or \code{None}. It should raise \exception{URLError}, unless a truly exceptional thing happens (for example, \exception{MemoryError} should not be mapped to \exception{URLError}). This method will be called before any protocol-specific open method. \end{methoddesc} \begin{methoddescni}[BaseHandler]{\var{protocol}_open}{req} This method is \emph{not} defined in \class{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 \class{OpenerDirector}. Return values should be the same as for \method{default_open()}. \end{methoddescni} \begin{methoddesc}[BaseHandler]{unknown_open}{req} This method is \var{not} defined in \class{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 \member{parent} \class{OpenerDirector}. Return values should be the same as for \method{default_open()}. \end{methoddesc} \begin{methoddesc}[BaseHandler]{http_error_default}{req, fp, code, msg, hdrs} This method is \emph{not} defined in \class{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 \class{OpenerDirector} getting the error, and should not normally be called in other circumstances. \var{req} will be a \class{Request} object, \var{fp} will be a file-like object with the HTTP error body, \var{code} will be the three-digit code of the error, \var{msg} will be the user-visible explanation of the code and \var{hdrs} will be a mapping object with the headers of the error. Return values and exceptions raised should be the same as those of \function{urlopen()}. \end{methoddesc} \begin{methoddesc}[BaseHandler]{http_error_\var{nnn}}{req, fp, code, msg, hdrs} \var{nnn} should be a three-digit HTTP error code. This method is also not defined in \class{BaseHandler}, but will be called, if it exists, on an instance of a subclass, when an HTTP error with code \var{nnn} occurs. Subclasses should override this method to handle specific HTTP