template files evaluation in python

Question

I am trying to use python for translating a set of templates to a set of configuration files based on values taken from a main configuration file. However, I am having certain issues. Consider the following example of a template file.

file1.cfg.template

%(CLIENT1)s %(HOST1)s  %(PORT1)d  C  %(COMPID1)s
%(CLIENT2)s %(HOST2)s  %(PORT2)d  C  %(COMPID2)s

This file contains an entry for each client. There are hundreds of config files like this and I don't want to have logic for each type of config file. Python should do the replacements and generate config files automatically given a set of global values read from a main xml config file. However, in the above example, if CLIENT2 does not exist, how do I delete that line? I expect Python would generate the config file using something like this:

os.open("file1.cfg.template").read() % myhash

where myhash is hash of configuration parameters from the main config file which may not contain CLIENT2 at all. In the case it does not contain CLIENT2, I want that line to disappear from the file. Is it possible to insert some 'IF' block in the file and have python evaluate it?

Thanks for your help. Any suggestions most welcome.

Answer 1

Sounds like you may have outgrown your originally simple home-grown templating solution. Maybe you should move to something like Jinja? It might be less of a headache to simply implement a third-party solution than it would be to create/continue to maintain your own solution.

Other options:

• cheetah
• mako

Answer 2

Maybe you can use a standalone Django template.

How do I use Django templates without the rest of Django? - Stack Overflow

Answer 3

Given that the files already exist, I would set default values for things like CLIENT2 (assuming you know ahead of time all possible keys). You can probably set the default value to something unusual so you can do

config = os.open("file1.cfg.template").read() % myhash
config = [l for l in config.split('\n') if <l does not have unusual text>].join('\n')

I agree with others that in the long term a more robust template would be better.