This module defines the class ConfigParser. The ConfigParser class implements a basic configuration file parser language which provides a structure similar to what you would find on Microsoft Windows INI files. You can use this to write Python programs which can be customized by end users easily.
Warning
This library does not interpret or write the value-type prefixes used in the Windows Registry extended version of INI syntax.
The configuration file consists of sections, led by a [section] header and followed by name: value entries, with continuations in the style of RFC 822 (see section 3.1.1, “LONG HEADER FIELDS”); name=value is also accepted. Note that leading whitespace is removed from values. The optional 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 and retrieval. Lines beginning with '#' or ';' are ignored and may be used to provide comments.
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.
Default values can be specified by passing them into the ConfigParser constructor as a dictionary. Additional defaults may be passed into the get() method which will override all others.
Sections are normally stored in a builtin dictionary. An alternative dictionary type can be passed to the ConfigParser constructor. For example, if a dictionary type is passed that sorts its keys, the sections will be sorted on write-back, as will be the keys within each section.
Derived class of RawConfigParser that implements the magical interpolation feature and adds optional arguments to the get() and items() methods. The values in defaults must be appropriate for the %()s string interpolation. Note that __name__ is an intrinsic default; its value is the section name, and will override any value provided in defaults.
All option names used in interpolation will be passed through the optionxform() method just like any other option name reference. For example, using the default implementation of optionxform() (which converts option names to lower case), the values foo %(bar)s and foo %(BAR)s are equivalent.
See also
RawConfigParser instances have the following methods:
Attempt to read and parse a list of filenames, returning a list of filenames which were successfully parsed. If filenames is a string, it is treated as a single filename. If a file named in filenames cannot be opened, that file will be ignored. This is designed so that you can specify a list of potential configuration file locations (for example, the current directory, the user’s home directory, and some system-wide directory), and all existing configuration files in the list will be read. If none of the named files exist, the ConfigParser instance will contain an empty dataset. An application which requires initial values to be loaded from a file should load the required file or files using readfp() before calling read() for any optional files:
import configparser, os
config = configparser.ConfigParser()
config.readfp(open('defaults.cfg'))
config.read(['site.cfg', os.path.expanduser('~/.myapp.cfg')])
The ConfigParser class extends some methods of the RawConfigParser interface, adding some optional arguments.
The SafeConfigParser class implements the same extended interface as ConfigParser, with the following addition:
An example of writing to a configuration file:
import configparser
config = configparser.RawConfigParser()
# When adding sections or items, add them in the reverse order of
# how you want them to be displayed in the actual file.
# In addition, please note that using RawConfigParser's and the raw
# mode of ConfigParser's respective set functions, you can assign
# non-string values to keys internally, but will receive an error
# when attempting to write to a file or when you get it in non-raw
# mode. SafeConfigParser does not allow such assignments to take place.
config.add_section('Section1')
config.set('Section1', 'int', '15')
config.set('Section1', 'bool', 'true')
config.set('Section1', 'float', '3.1415')
config.set('Section1', 'baz', 'fun')
config.set('Section1', 'bar', 'Python')
config.set('Section1', 'foo', '%(bar)s is %(baz)s!')
# Writing our configuration file to 'example.cfg'
with open('example.cfg', 'wb') as configfile:
config.write(configfile)
An example of reading the configuration file again:
import configparser
config = configparser.RawConfigParser()
config.read('example.cfg')
# getfloat() raises an exception if the value is not a float
# getint() and getboolean() also do this for their respective types
float = config.getfloat('Section1', 'float')
int = config.getint('Section1', 'int')
print(float + int)
# Notice that the next output does not interpolate '%(bar)s' or '%(baz)s'.
# This is because we are using a RawConfigParser().
if config.getboolean('Section1', 'bool'):
print(config.get('Section1', 'foo'))
To get interpolation, you will need to use a ConfigParser or SafeConfigParser:
import configparser
config = configparser.ConfigParser()
config.read('example.cfg')
# Set the third, optional argument of get to 1 if you wish to use raw mode.
print(config.get('Section1', 'foo', 0)) # -> "Python is fun!"
print(config.get('Section1', 'foo', 1)) # -> "%(bar)s is %(baz)s!"
# The optional fourth argument is a dict with members that will take
# precedence in interpolation.
print(config.get('Section1', 'foo', 0, {'bar': 'Documentation',
'baz': 'evil'}))
Defaults are available in all three types of ConfigParsers. They are used in interpolation if an option used is not defined elsewhere.
import configparser
# New instance with 'bar' and 'baz' defaulting to 'Life' and 'hard' each
config = configparser.SafeConfigParser({'bar': 'Life', 'baz': 'hard'})
config.read('example.cfg')
print(config.get('Section1', 'foo')) # -> "Python is fun!"
config.remove_option('Section1', 'bar')
config.remove_option('Section1', 'baz')
print(config.get('Section1', 'foo')) # -> "Life is hard!"
The function opt_move below can be used to move options between sections:
def opt_move(config, section1, section2, option):
try:
config.set(section2, option, config.get(section1, option, 1))
except configparser.NoSectionError:
# Create non-existent section
config.add_section(section2)
opt_move(config, section1, section2, option)
else:
config.remove_option(section1, option)