How To Use Variables Already Defined In Configparser

I'm using ConfigParser in Python config.ini is [general] name: my_name base_dir: /home/myhome/exp exe_dir: ${base_dir}/bin Here I want exp_dir becomes /home/myhome/exp/bin not ${

Solution 1:

You can use ConfigParser interpolation

On top of the core functionality, SafeConfigParser supports interpolation. This means values can contain format strings which refer to other values in the same section, or values in a special DEFAULT section. Additional defaults can be provided on initialization.

For example:

[My Section] 
foodir: %(dir)s/whatever 
dir=frob 
long: this value continues    
    in the next line 

would resolve the %(dir)s to the value of dir (frob in this case). All reference expansions are done on demand.

Your example becomes:

[general]
name: my_namebase_dir: /home/myhome/expexe_dir: %(base_dir)s/bin

Solution 2:

Instead of "${foo}", write "%(foo)s". (See http://docs.python.org/library/configparser.html and search for "interpolation". This works for either an ordinary ConfigParser or a SafeConfigParser.)

Solution 3:

In Python 3, you can use ${base_dir}/bin, and the extended interpolation allows you to use variables from other sections. Example:

[Common]
home_dir: /Userslibrary_dir: /Librarysystem_dir: /Systemmacports_dir: /opt/local

[Frameworks]
Python: 3.2path: ${Common:system_dir}/Library/Frameworks/

[Arthur]
nickname: Two Shedslast_name: Jacksonmy_dir: ${Common:home_dir}/twoshedsmy_pictures: ${my_dir}/Picturespython_dir: ${Frameworks:path}/Python/Versions/${Frameworks:Python}