You want to read configuration files written in the common .ini configuration file

format.

The configparser module can be used to read configuration files. For example, suppose

you have this configuration file:

; config.ini

; Sample configuration file

[installation]

library=%(prefix)s/lib

include=%(prefix)s/include

bin=%(prefix)s/bin

prefix=/usr/local

# Setting related to debug configuration

[debug]

log_errors=true

show_warnings=False

[server]

port: 8080

nworkers: 32

pid-file=/tmp/spam.pid

root=/www/root

signature:

=================================

=================================

Here is an example of how to read it and extract values:

>>> from configparser import ConfigParser

>>> cfg = ConfigParser()

>>> cfg.read('config.ini')

>>> cfg.sections()

>>> cfg.get('installation','library')

>>> cfg.getboolean('debug','log_errors')

True

>>> cfg.getint('server','port')

>>> cfg.getint('server','nworkers')

>>> print(cfg.get('server','signature'))

\=================================

Brought to you by the Python Cookbook

\=================================

>>>

If desired, you can also modify the configuration and write it back to a file using the

cfg.write() method. For example:

>>> cfg.set('server','port','9000')

>>> cfg.set('debug','log_errors','False')

>>> import sys

>>> cfg.write(sys.stdout)

[debug]

log_errors = False

show_warnings = False

[server]

port = 9000

nworkers = 32

pid-file = /tmp/spam.pid

root = /www/root

signature =

=================================

Brought to you by the Python Cookbook

=================================

>>>

Configuration files are well suited as a human-readable format for specifying configu‐

ration data to your program. Within each config file, values are grouped into different

sections (e.g., “installation,” “debug,” and “server,” in the example). Each section then

specifies values for various variables in that section.

There are several notable differences between a config file and using a Python source

file for the same purpose. First, the syntax is much more permissive and “sloppy.” For

example, both of these assignments are equivalent:

The names used in a config file are also assumed to be case-insensitive. For example:

>>> cfg.get('installation','PREFIX')

>>> cfg.get('installation','prefix')

>>>

When parsing values, methods such as getboolean() look for any reasonable value.

For example, these are all equivalent:

Perhaps the most significant difference between a config file and Python code is that,

unlike scripts, configuration files are not executed in a top-down manner. Instead, the

file is read in its entirety. If variable substitutions are made, they are done after the fact.

For example, in this part of the config file, it doesn’t matter that the prefix variable is

assigned after other variables that happen to use it:

An easily overlooked feature of ConfigParser is that it can read multiple configuration

files together and merge their results into a single configuration. For example, suppose

a user made their own configuration file that looked like this:

This file can be merged with the previous configuration by reading it separately. For

example:

>>> # Previously read configuration

>>> cfg.get('installation', 'prefix')

>>> # Merge in user-specific configuration

>>> import os

>>> cfg.read(os.path.expanduser('~/.config.ini'))

>>> cfg.get('installation', 'prefix')

>>> cfg.get('installation', 'library')

>>> cfg.getboolean('debug', 'log_errors')

>>>

Observe how the override of the prefix variable affects other related variables, such as

the setting of library. This works because variable interpolation is performed as late

as possible. You can see this by trying the following experiment:

>>> cfg.get('installation','library')

>>> cfg.set('installation','prefix','/tmp/dir')

>>> cfg.get('installation','library')

>>>

Finally, it’s important to note that Python does not support the full range of features you

might find in an .ini file used by other programs (e.g., applications on Windows). Make

sure you consult the configparser documentation for the finer details of the syntax

and supported features.