Python Config Parser environment variables

Question

I am trying to read some environment variables into my ConfigParser file.

I was referring to this answer but I am getting

"InterpolationDepthError: Value interpolation too deeply recursive" error.
section: [amazon]
    option : amazon_access_key
    rawval : %(AMAZON_ACCESS_KEY)s

Here is the portion of my config file:

[amazon]
amazon_access_key=%(AMAZON_ACCESS_KEY)s
amazon_secret_key=%(AMAZON_SECRET_KEY)s

And this is what I am writing to call the file:

from ConfigParser import SafeConfigParser
import os

config = SafeConfigParser(os.environ)
config.read('config.txt')

When I am calling these variables directly in the "amazon" section, I get the above stated error.

When I call these variables in the "default" section, like:

[default]
aws_access_key=%(AMAZON_ACCESS_KEY)s
aws_secret_key=%(AMAZON_SECRET_KEY)s

[amazon]
    amazon_access_key=%(aws_access_key)s
    amazon_secret_key=%(aws_secret_key)s

I get the following error:

ConfigParser.InterpolationMissingOptionError: Bad value substitution:
    section: [amazon]
    option : amazon_access_key
    key    : aws_access_key
    rawval : %(aws_access_key)s

What am I missing here?

Also, how can I have separate config files for local and production deployments? Currently, all the configurations are same for local and production environments.

Answer 1

from ConfigParser import SafeConfigParser
import ConfigParser
import os
class CaseConfigParser(SafeConfigParser):
     def optionxform(self, optionstr):
         return optionstr
config = CaseConfigParser(os.environ)
config.read('config.ini')
print config.get('amazon', 'amazon_access_key')

Explanation: The problem here is with optionxform, which turns all options to lower case by default. eventually, it will have key and value equal, similar to following.

[amazon]
amazon_access_key=%(amazon_access_key)s

Another solution can be - change names of keys in config.txt NOT equal to env vars.

[amazon]
aak=%(AMAZON_ACCESS_KEY)s

and then

config = SafeConfigParser(os.environ)
config.read('config.ini')
print config.get('amazon', 'aak')