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To: python-list@python.org
From: Peter Otten <__peter__@web.de>
Subject: Re: Need to write python source with python
Date: Tue, 28 Feb 2012 20:25:33 +0100
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crstop@gmail.com wrote:

> On Tuesday, February 28, 2012 9:56:43 AM UTC-8, Peter Otten wrote:
>> crstop@gmail.com wrote:
>> 
>> > I'm new to Python but have experience with a few other programming
>> > languages(Java, Perl, JavaScript).
>> > 
>> > I'm using Python 2.7.2 and I'm trying to create and write to a file
>> > (.py) a python class and functions from python. I will also need to
>> > later read and edit the file. I realize I could just write strings
>> > using the available string and file writing methods but suspect there
>> > is a better way than that.
>> > 
>> > I have read about pickle, ast, and Django; searched this group and the
>> > web but haven't found a solution that seems to fit. Any suggestion?
>> 
>> Due to Python's dynamic nature it is rarely necessary to generate Python
>> code. What are you actually trying to achieve?
> 
> I'm trying to generate the script file that will launch a PythonCard
> resource file.
> 
> very basic example from the documentation.
> 
>     #!/usr/bin/python
>     """
>     __version__ = "$Revision: 1.10 $"
>     __date__ = "$Date: 2004/04/24 22:13:31 $"
>     """
> 
>     from PythonCard import model
>     
>     class Minimal(model.Background):
>         pass
>     
>     if __name__ == '__main__':
>         app = model.Application(Minimal)
>         app.MainLoop()

If it doesn't get too complex you could start with Python's built-in string 
formatting:

import sys

template = '''\
#!/usr/bin/python
from PythonCard import model

class {Class}(model.Background):
    pass

if __name__ == '__main__':
    app = model.Application({Class})
    app.MainLoop()
'''

resourcename, filename = sys.argv[1:]

with open(resourcename, "U") as f:
    data = eval(f.read())

with open(filename, "w") as f:
    f.write(template.format(Class=data["application"]["name"]))

If you need logic inside the template, here's on overview: 

http://wiki.python.org/moin/Templating

So there are rather too many options than too few.