[Medusa-dev] psp_handler - embed python in HTML like ASP

Kevin Smith

Sun Apr 27 13:27:49 EDT 2003

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Hi, I have created a psp_handler (Python Server Pages???) for medusabased on the script_handler.  This handler lets you mix HTML with pythonlike ASP pages.  The handler can be installed on the server in the sammanner as the script handler.  Here is an example hello.psp file...Medusa PSP Handler<%pspprint "hello world"%>I have been using this handler for much more useful applications ofcourse :).  Just wrap the inline python with <%psp ... %> tags. Here is the handler...# -*- Mode: Python -*-# This is a simple python server pages script handler.# A note about performance: This is really only suited for 'fast'# scripts: The script should generate its output quickly, since the# whole web server will stall otherwise.  This doesn't mean you have# to write 'fast code' or anything, it simply means that you shouldn't# call any long-running code, [like say something that opens up an# internet connection, or a database query that will hold up the# server].  If you need this sort of feature, you can support it using# the asynchronous I/O 'api' that the rest of medusa is built on.  [or# you could probably use threads]# Put your script into your web docs directory (like a cgi-bin# script), make sure it has the correct extension [see the overridable# script_handler.extension member below].## There's lots of things that can be done to tweak the restricted# execution model.  Also, of course you could just use 'execfile'# instead (this is now the default, see class variable# script_handler.restricted)import rexecimport reimport stringimport StringIOimport sysimport counterimport default_handlerimport producersfrom script_handler import collectorunquote    = default_handler.unquotedef iif(expression,truepart,falsepart):    if expression:        return truepart    else:        return falsepartclass psp_handler:     extension = 'psp'    # the following should not get overridden!    fp = None    script = ''    data = ''    insidePsp = False        script_regex = re.compile (            r'.*/([^/]+\.%s)' % extension,            re.IGNORECASE            )    def __init__ (self,filesystem,restricted=False,preserveNamespace=True):        self.filesystem = filesystem        self.hits = counter.counter()        self.exceptions = counter.counter()        self.restricted = restricted        self.preserveNamespace = preserveNamespace    def match (self, request):        [path, params, query, fragment] = request.split_uri()        m = self.script_regex.match (path)        return (m and (m.end() == len(path)))    def handle_request (self, request):        [path, params, query, fragment] = request.split_uri()        while path and path[0] == '/':            path = path[1:]        if '%' in path:            path = unquote (path)        if not self.filesystem.isfile (path):            request.error (404)            return        else:            self.hits.increment()            request.script_filename = self.filesystem.translate (path)            if request.command in ('PUT', 'POST'):                # look for a Content-Length header.                cl = request.get_header ('content-length')                length = int(cl)                if not cl:                    request.error (411)                else:                    collector (self, length, request)            else:                self.continue_request (                        request,                        StringIO.StringIO() # empty stdin                        )    def continue_request (self, request, stdin):        temp_files = stdin, StringIO.StringIO(), StringIO.StringIO()        old_files = sys.stdin, sys.stdout, sys.stderr        try:            sys.request = request            sys.stdin, sys.stdout, sys.stderr = temp_files            try:                #get the path from the uri and open the file with thefilesystem class                try:                    file =self.filesystem.open(request.split_uri()[0],'r')                except IOError:                    request.error (404)                    return                self.fp = producers.file_producer(file)                self.dissect_psp(request)                request.reply_code = 200            except:                request.reply_code = 500                self.exceptions.increment()        finally:            sys.stdin, sys.stdout, sys.stderr = old_files            del sys.request        i,o,e = temp_files        if request.reply_code != 200:            s = e.getvalue()        else:            s = o.getvalue()        request['Content-Length'] = len(s)        request.push (s)        request.done()    def status (self):        return producers.simple_producer (                'PSP - Python Server Pages Handler'                + '
         
          '                + '  
          Hits: %s' % self.hits                + '  
          Exceptions: %s' % self.exceptions                + '  
          Execution Mode:%s' %iif(self.restricted,'Restricted','Unrestricted' )                + '  
          Namespace::%sPreserved' %iif(self.preserveNamespace,'','not ' )                + '
         
'                )    ## this function reads the file using the file producer and sends      ## the data to the client until the script start tag '<%psp'    ## is found.  All of the text between the script start marker     ## '<%psp' and the end script marker '%>' is executed as    ## python script.     def dissect_psp(self,request):        self.insidePsp = False        self.script = ''        while not self.fp.done:            self.data=self.fp.more()            #print the HTML to the stdout, execute the python script...            while self.data:                if self.insidePsp:                    sectiοnend=self.data.find("%>")                    if (sectionend == -1):                        #end of script section is not in the currentchunk                        self.script += self.data                        self.data = ''                    else:                        #end of script section is within the currentchunk                        self.script += self.data[:sectionend]                        self.data = self.data[sectionend+len("%>"):]                        del sectionend                        if self.preserveNamespace:                            if self.restricted:                                r = rexec.RExec()                            try:                                if self.restricted:                                    r.s_exec (self.script)                                else:                                    exec (self.script)                                request.reply_code = 200                            except:                                request.reply_code = 500                                self.exceptions.increment()                        else:                            self.script_exec(request,self.script)                        self.script = ''                        self.insidePsp = False                else:                    sectiοnend=self.data.find("<%psp")                    if (sectionend == -1):                        #end of HTML section is not in the current chunk                        print self.data                        self.data = ''                    else:                        #end of HTML section is within the current chunk                        print self.data[:sectionend]                        self.data = self.data[sectionend+len("<%psp"):]                        self.insidePsp = True                                               # this function will eliminate any of the unnecessary objects    # from appearing in the script namespace.  print dir() should    # return only self,request, and script.    # one drawback with this method is that namespace is cleared    # for each section of script in the document.        def script_exec(self,request,script):        # for debugging we can send a copy of the script to the browser.        # this presents security issues so this next line should be        # commented out.        if self.restricted:            r = rexec.RExec()        try:            if self.restricted:                r.s_exec (script)            else:                exec (script)            request.reply_code = 200        except:            request.reply_code = 500            self.exceptions.increment()