konfig 1.1

Usage

>>> from konfig import Config
>>> c = Config('myconfig.ini')

Then read configparser’s documentation for the APIs.

Konfig as some extra APIs like as_args(), which will return the config file as argparse compatible arguments:

>>> c.as_args()
['--other-stuff', '10', '--httpd', '--statsd-endpoint', 'http://ok']

For automatic filtering, you can also pass an argparse parser object to scan_args(). I will iterate over the arguments you’ve defined in the parser and look for them in the config file, then return a list of args like as_args(). You can then use this list directly with parser.parse_args() - or complete it with sys.argv or whatever.

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--log-level', dest='loglevel')
>>> parser.add_argument('--log-output', dest='logoutput')
>>> parser.add_argument('--daemon', dest='daemonize', action='store_true')

>>> config = Config('myconfig.ini')
>>> args_from_config = config.scan_args(parser)

>>> parser.parse_args(args=sys.argv[1:]+args_from_config)

Syntax Definition

The configuration file is a ini-based file. (See http://en.wikipedia.org/wiki/INI_file for more details.) Variables name can be assigned values, and grouped into sections. A line that starts with “#” is commented out. Empty lines are also removed.

Example:

[section1]
# comment
name = value
name2 = "other value"

[section2]
foo = bar

Ini readers in Python, PHP and other languages understand this syntax. Although, there are subtle differences in the way they interpret values and in particular if/how they convert them.

Values conversion

Here are a set of rules for converting values:

• If value is quoted with “ chars, it’s a string. This notation is useful to include “=” characters in the value. In case the value contains a “ character, it must be escaped with a “" character.

• When the value is composed of digits and optionally prefixed by “-”, it’s tentatively converted to an integer or a long depending on the language. If the number exceeds the range available in the language, it’s left as a string.

• If the value is “true” or “false”, it’s converted to a boolean, or 0 and 1 when the language does not have a boolean type.

• A value can be an environment variable : “${VAR}” is replaced by the value of VAR if found in the environment. If the variable is not found, an error must be raised.

• A value can contains multiple lines. When read, lines are converted into a sequence of values. Each new line for a multiple lines value must start with a least one space or tab character.

Examples:

[section1]
# comment
a_flag = True
a_number = 1
a_string = "other=value"
another_string = other value
a_list = one
         two
         three
user = ${USERNAME}

Extending a file

An INI file can extend another file. For this, a “DEFAULT” section must contain an “extends” variable that can point to one or several INI files which will be merged to the current file by adding new sections and values.

If the file pointed in “extends” contains section/variable names that already exist in the original file, they will not override existing ones.

Here’s an example: you have a public config file and want to keep some database passwords private. You can have those password in a separate file.

public.ini:

[database]
user = tarek
password = PUBLIC

[section2]
foo = baz
bas = bar

And then in private.ini:

[DEFAULT]
extends = public.ini

[database]
password = secret

Now if you use private.ini you will get:

[database]
user = tarek
password = secret

[section2]
foo = baz
bas = bar

To point several files, the multi-line notation can be used:

[DEFAULT]
extends = public1.ini
          public2.ini

When several files are provided, they are processed sequentially. So if the first one has a value that is also present in the second, the second one will be ignored. This means that the configuration goes from the most specialized to the most common.

Override mode

If you want to extend a file and have existing values overridden, you can use “overrides” instead of “extends”.

Here’s an example. file2.ini:

[section1]
name2 = "other value"

[section2]
foo = baz
bas = bar

file1.ini:

[DEFAULT]
overrides = file2.ini

[section2]
foo = bar

Result if you use file1.ini:

[section1]
name2 = "other value"

[section2]
foo = baz
bas = bar

In section2, notice that foo is now baz.