[mod_python] mod_python weirdness, maybe related to importing?

Sean Reifschneider jafo at tummy.com
Mon Jun 9 23:59:27 EST 2003

I've been trying to build a web application system using mod_python, and
I've been running into some weirdness.  Some of it is just sporadic
behavior, some of it seems to be pretty consistent.  Before I get
started, my main development system is running Red Hat 9 with Python
2.2.2 and I've been trying mod_python 3.0.1 (shipped with RH9) and

Basically, I'm building up a package that contains my system.  In it I
have a module which contains my handler:

   AddHandler python-program .html
   PythonHandler jotweb.jotweb_mod_python::handler

Basically, my handler is using SimpleTAL to parse some HTML, which will
result in my code getting called, which will import things from the
jotweb package:

   fileName = path + '.py'
   fp = open(fileName, 'r')
   module = imp.load_source(path, fileName, fp)

So, basically, I am trying to load a module from a specific file.

The first problem I'm seeing is that imports are just weird.  For
example, if I have code which does "import jotweb.input.Request",
unless my __init__.py in jotweb/input includes:

   import Request

I will get an error to the effect that the module object contains no
element "Request".  Of course, from a regular Python program, I can do
"import jotweb.input.Request" just fine either way.

Basically, because of the above, my entire code-base has to be imported
when you do an "import jotweb".

Further, I'm running into weird issues with headers_out.  If from my
jotweb_mod_python.handler code I do:

   req.headers_out.add('key', 'value')

it will properly add the specified header.  And if this code is executed
from the module that is imported as above, it seems to work.  If,
however, in this imported module I do:

   import jotweb

where "processLogin()" gets a handle to the request object and does
req.headers_out.add(), the headers aren't showing up in my browser.
HOWEVER, if I telnet to port 80 and issue a GET request to exactly the
same URL that I issued in the GET request, the headers are *NOT* getting
return as far as I can tell (no cookie is getting set, doing "View
Documenat Information" shows not those headers, but if I set headers in
my main mod_python handler, it WILL show it.

I've verified that the call to headers_out.add() is happening by adding
a syslog before it, it's definitely calling that code.

It seems like at some point something is making it so that
headers_out.add() doesn't work any more.  Would pulling the form data
out of the request cause that?  Any thoughts on why the imports seem to
work quite differently on a name-space basis from how they happen from
the interpreter:

   AttributeError: 'module' object has no attribute 'input'

Is there something about being in mod_python that makes it a "toy"
interpreter in some ways, that mean I'm constantly going to be bumping
into weird things?


 I like to be different, so I built a lowercase a-frame house.
                 -- Sean Reifschneider, 2000
Sean Reifschneider, Inimitably Superfluous <jafo at tummy.com>
tummy.com, ltd. - Linux Consulting since 1995.  Qmail, Python, SysAdmin

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