Creating your own mod_python request dispatcher

Creating your own mod_python request dispatcher that maps url's to python request handlers.

Conceptually I have something that looks like this:

 +-------------+
 | Clients     |
 | Web Browser |
 +-------------+
   | [http://somecooldomain.com/coorequest]
   |  ^ 
   |  | [Cool Response] 
   V  |
 +--------+     +------------+     +---------------+     +---------+
 | Apache | --> | Mod_Python | --> | dispatcher.py | --> | cool.py | --+
 | (A)    | <-- |            | <-- | (B)           |     | (D)     |   |
 +--------+     +------------+     +---------------+     +---------+   |    
                                        |     ^                        |
                                        |     |                        |
                                        |     +------------------------+
                                        V
                                    +-------------+
                                    | urlmap.conf |
                                    | (C)         |
                                    +-------------+

A) Apache Configuration:
On my server I have mod_python set up to handle any request that comes in without a file extension. That way I can have those cool REST style URI's. I use the apache "FilesMatch" directive in my httpd.conf file to look for any request that does not contain a '.' before the '?' in the query string:

 <FilesMatch "(^[^\.]*$|^[^\?]*[\?]+[^$]+$)">
    SetHandler python-program
    PythonHandler common.dispatch.dispatcher
    PythonDebug On
  </FilesMatch>

B) dispatcher.py
The source for dispatcher.py can be found here.

C) Example urlmap.conf

[somecooldomain.com]
/=cooldomain.handlers.home.handler
/signup=cooldomain.handlers.member.signup
/login=cooldomain.handlers.member.login
/logout=cooldomain.handlers.member.logout
/cool=cooldomain.handlers.cool.handler

D) cool.py
This is the handler that generates your content. In my content handlers I usually do things like query the database, process business logic, select a cheetah template and return the result as html.

In summary I use this approch for a couple of reasons, first it allows me to decouple my url's from my python code that way I don't have python code + html sitting around in the same directory. Secondly I get one piece of code that handles every request. (good for sessions and things like that)

urlencoder/decoder for python

EDIT (I so stand corrected.):

I could have just used:
urllib.quote
urllib.unquote

---------------------------------------------------

Every once and a while I run into the need for a urlencoder/decoder function that just accepts a string and returns a string.

The one that comes w/ urllib(2) takes a dictionary and returns a "name=val" formatted string.
My only problem is that it does 2 things at once:
1) url encodes.
2) constructs a query or post string.

So I wrote a quick utility to do just #1:

_keys = [
 "$", "&", "+", ",", "/", ":", ";", "=", "?", "@", " ", '"',
 "<", ">", "#", "%", "{", "}", "|", "\\", "^", "~", "[", "]", "`"]

_vals = [
 '%24', '%26', '%2B', '%2C', '%2F', '%3A', '%3B', '%3D', '%3F',
 '%40', '%20', '%22', '%3C', '%3E', '%23', '%25', '%7B', '%7D',
 '%7C', '%5C', '%5E', '%7E', '%5B', '%5D', '%60']

def encode(str=""):
 """ URL Encodes a string with out side effects
 """
 return "".join([_swap(x) for x in str])

def decode(str=""):
 """ Takes a URL encoded string and decodes it with out side effects
 """
 if not str: return None
 for v in _vals:
   if v in str: str = str.replace(v, _keys[_vals.index(v)])
 return str

def _swap(x):
 """ Helper function for encode.
 """
 if x in _keys: return _vals[_keys.index(x)]
 return x

### units ###
if __name__ == "__main__":
 assert("".join(_keys) == decode(encode("".join(_keys))))
 assert("".join(_vals) == encode(decode("".join(_vals))))
 print "passed all unit tests."