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.
Note
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.
Configuration files may include comments, prefixed by specific characters (# and ;). Comments may appear on their own in an otherwise empty line, or may be entered in lines holding values or spection names. In the latter case, they need to be preceded by a whitespace character to be recognized as a comment. (For backwards compatibility, only ; starts an inline comment, while # does not.)
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.
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 built-in 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.
The basic configuration object. When defaults is given, it is initialized into the dictionary of intrinsic defaults. When dict_type is given, it will be used to create the dictionary objects for the list of sections, for the options within a section, and for the default values. This class does not support the magical interpolation behavior.
Changed in version 3.1: The default dict_type is collections.OrderedDict.
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.
Changed in version 3.1: The default dict_type is collections.OrderedDict.
Derived class of ConfigParser that implements a more-sane variant of the magical interpolation feature. This implementation is more predictable as well. New applications should prefer this version if they don’t need to be compatible with older versions of Python.
Changed in version 3.1: The default dict_type is collections.OrderedDict.
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')])
Read and parse configuration data from the file or file-like object in fp (only the readline() method is used). The file-like object must operate in text mode, i.e. return strings from readline().
If filename is omitted and fp has a name attribute, that is used for filename; the default is <???>.
Transforms the option name option as found in an input file or as passed in by client code to the form that should be used in the internal structures. The default implementation returns a lower-case version of option; subclasses may override this or client code can set an attribute of this name on instances to affect this behavior.
You don’t necessarily need to subclass a ConfigParser to use this method, you can also re-set it on an instance, to a function that takes a string argument. Setting it to str, for example, would make option names case sensitive:
cfgparser = ConfigParser()
...
cfgparser.optionxform = str
Note that when reading configuration files, whitespace around the option names are stripped before optionxform() is called.
The ConfigParser class extends some methods of the RawConfigParser interface, adding some optional arguments.
Get an option value for the named section. If vars is provided, it must be a dictionary. The option is looked up in vars (if provided), section, and in defaults in that order.
All the '%' interpolations are expanded in the return values, unless the raw argument is true. Values for interpolation keys are looked up in the same manner as the option.
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', 'w') 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)