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

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

Kevin Smith smithk at attbi.com
Sun Apr 27 13:27:49 EDT 2003

 

Hi, I have created a psp_handler (Python Server Pages???) for medusa

based on the script_handler.  This handler lets you mix HTML with python

like ASP pages.  The handler can be installed on the server in the sam

manner as the script handler.

Here is an example hello.psp file...

<html>

<title>Medusa PSP Handler</title>

<body>

<%psp

print "hello world"

%>

</body>

</html>

I have been using this handler for much more useful applications of

course :).  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 rexec

import re

import string

import StringIO

import sys

import counter

import default_handler

import producers

from script_handler import collector

unquote    = default_handler.unquote

def iif(expression,truepart,falsepart):

    if expression:

        return truepart

    else:

        return falsepart

class 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 the

filesystem 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 (

                '<li>PSP - Python Server Pages Handler'

                + '<ul>'

                + '  <li><b>Hits:</b> %s' % self.hits

                + '  <li><b>Exceptions:</b> %s' % self.exceptions

                + '  <li><b>Execution Mode:</b>%s' %

iif(self.restricted,'Restricted','Unrestricted' )

                + '  <li><b>Namespace:</b>:%sPreserved' %

iif(self.preserveNamespace,'','not ' )

                + '</ul>'

                )

    ## 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:

                    sectionend=self.data.find("%>")

                    if (sectionend == -1):

                        #end of script section is not in the current

chunk

                        self.script += self.data

                        self.data = ''

                    else:

                        #end of script section is within the current

chunk

                        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:

                    sectionend=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()


 

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