Interoperability between VB and Python under ASP

M

Max Ischenko

Hi,

I've started to develop under Microsoft ASP framework, which allows
different lang. used in a ActiveX page. I wonder about possible
strategies to use Python modules from VBScript <%%> includes.

Right now I'm thinking about this approaches:
- create a COM server in Python to be able to call it from VB.
Drawbacks: cumbersome and (probably) slow.
- pure data exchange. Python code sets some data in global env. that is
afterwards read by VB. Drawbacks: very limited in nature.
- convert all VB pieces that need access to Python modules into Python.

Have I missed something or could anyone comment on this?
Discussion is wellcomed.
 
B

bigdog

Max Ischenko said:
Hi,

I've started to develop under Microsoft ASP framework, which allows
different lang. used in a ActiveX page. I wonder about possible
strategies to use Python modules from VBScript <%%> includes.

Right now I'm thinking about this approaches:
- create a COM server in Python to be able to call it from VB.
Drawbacks: cumbersome and (probably) slow.
- pure data exchange. Python code sets some data in global env. that is
afterwards read by VB. Drawbacks: very limited in nature.
- convert all VB pieces that need access to Python modules into Python.

Have I missed something or could anyone comment on this?
Discussion is wellcomed.

I've mostly done option 3, converting what I needed to Python. It
results in a lot cleaner code (you can't mix html elements and code
very well, for example, in vb you can put a for loop around a section
of HTML, whereas in Python you can't) and the time it took to convert
the code (not much, really, it's a pretty clean port in most cases)
has been more than paid back in maintainability.

Another thing I've done, rather than just port all the code in a given
piece, is to find things I can modularize and then move only the
pieces to Python that I think make sense. For example, I've got a page
set up that you can dynamically add content to, kind of like a wiki,
but much more structured. The only part that is in Python is the
script that edits the HTML file, as file access and manipulation is so
much easier in Python than in an VBScript. All of the user elements
are either in straight html pages or in asp with vbscript. I post my
results to the Python page, update the file, then Response.Redirect to
the page I'm interested in viewing after the file is updated.

I think your next best bet is creating COM servers, or perhaps using
Python within a CGI app for particular pieces of logic. I would avoid
the data exchange route.

I don't know if this will help, but it might be worth a shot.
http://vb2py.sourceforge.net/ I've never used it myself, I only point
it out as a curiosity I've heard of
 
P

Paul Paterson

bigdog said:
I don't know if this will help, but it might be worth a shot.
http://vb2py.sourceforge.net/ I've never used it myself, I only point
it out as a curiosity I've heard of

Although it isn't (currently) targetted at VBScript, the CVS version of
vb2py might help if you have reasonably sized blocks of VBScript code to
convert. It hasn't been tested on VBScipt specifically but the parser
should work for most things and I'd certainly be interested to hear of
any specific problems with ASP scripts.

Out of the box it won't even recognize code in a .asp page, but I threw
together the following code. I'm not an expert on ASP or VBScript but
even if this is not correct it might point you in the right direction if
you want to try a convert-to-python route ....

test = """
<html>
<%

function factorial(x)
if x = 0 then
factorial = 1
else
factorial = x*factorial(x-1)
end if
end function

%>
</html>
"""

from vb2py.vbparser import parseVB, VBCodeModule
import re

def translateScript(match):
"""Translate VBScript fragment to Python"""
block = parseVB(match.groups()[0], container=VBCodeModule())
return "<%%\n%s\n%%>" % block.renderAsCode()

converter = re.compile(r"\<%(.*?)%\>", re.DOTALL + re.MULTILINE)
print converter.sub(translateScript, test)


.... which should output:

"""
<html>
<%
from vb2py.vbfunctions import *

def factorial(x):
if x == 0:
_ret = 1
else:
_ret = x * factorial(x - 1)
return _ret

%>
</html>
"""

You'll need the CVS version to get this to work - the v0.1.1 doesn't
have the full parser and the v0.2 release is a couple of weeks off yet.

If you do decide to try this route, I'd be very interested to hear of
any specific issues that come up with translating ASP/VBScript to Python.


Paul

=========================
Paul Paterson

vb2py :: A Visual Basic to Python Conversion Toolkit
http://vb2py.sourceforge.net
 
M

Max Ischenko

I've mostly done option 3, converting what I needed to Python. It
results in a lot cleaner code (you can't mix html elements and code
very well, for example, in vb you can put a for loop around a section
of HTML, whereas in Python you can't) and the time it took to convert
the code (not much, really, it's a pretty clean port in most cases)
has been more than paid back in maintainability.

That's sounds encouraging, thanks. I'd probably go this route.
 
M

Max Ischenko

Paul said:
Although it isn't (currently) targetted at VBScript, the CVS version of
vb2py might help if you have reasonably sized blocks of VBScript code to
convert. It hasn't been tested on VBScipt specifically but the parser
should work for most things and I'd certainly be interested to hear of
any specific problems with ASP scripts.

That's seems like an interesting idea!
While I doubt that the conversion could (or, more appopriately, should)
be done automatically, I'll check out your project, thanks.
If you do decide to try this route, I'd be very interested to hear of
any specific issues that come up with translating ASP/VBScript to Python.

OK.
 
M

Max Ischenko

Another thing I've done, rather than just port all the code in a given
piece, is to find things I can modularize and then move only the
pieces to Python that I think make sense. For example, I've got a page
set up that you can dynamically add content to, kind of like a wiki,
but much more structured. The only part that is in Python is the
script that edits the HTML file, as file access and manipulation is so
much easier in Python than in an VBScript. All of the user elements
are either in straight html pages or in asp with vbscript. I post my
results to the Python page, update the file, then Response.Redirect to
the page I'm interested in viewing after the file is updated.

I got a question on this issue.
When modularizing Python code, how does one handle data exchange between
Python snippets?

I mean, you can't store anything complicated in a Session (for
instance). Yeah, I can pickle/unpickle any Python object but that feels
like a kludge. Should I setup some global hash, keyed by SessionID to
store data there?
 

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