13.2. ConfigParser — Configuration file parser

Note

The ConfigParser module has been renamed to configparser in Python 3. The 2to3 tool will automatically adapt imports when converting your sources to Python 3.

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.

See also

Module shlex

Support for creating Unix shell-like mini-languages which can be used as an alternate format for application configuration files.

Module json

The json module implements a subset of JavaScript syntax which can also be used for this purpose.

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 section 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.

class ConfigParser.RawConfigParser([defaults[, dict_type[, allow_no_value]]])

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. When allow_no_value is true (default: False), options without values are accepted; the value presented for these is None.

This class does not support the magical interpolation behavior.

All option names are passed through the optionxform() method. Its default implementation converts option names to lower case.

New in version 2.3.

Changed in version 2.6: dict_type was added.

Changed in version 2.7: The default dict_type is collections.OrderedDict. allow_no_value was added.

class ConfigParser.ConfigParser([defaults[, dict_type[, allow_no_value]]])

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. Using the default implementation of optionxform(), the values foo %(bar)s and foo %(BAR)s are equivalent.

New in version 2.3.

Changed in version 2.6: dict_type was added.

Changed in version 2.7: The default dict_type is collections.OrderedDict. allow_no_value was added.

class ConfigParser.SafeConfigParser([defaults[, dict_type[, allow_no_value]]])

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.

New in version 2.3.

Changed in version 2.6: dict_type was added.

Changed in version 2.7: The default dict_type is collections.OrderedDict. allow_no_value was added.

exception ConfigParser.Error

Base class for all other configparser exceptions.

exception ConfigParser.NoSectionError

Exception raised when a specified section is not found.

exception ConfigParser.DuplicateSectionError

Exception raised if add_section() is called with the name of a section that is already present.

exception ConfigParser.NoOptionError

Exception raised when a specified option is not found in the specified section.

exception ConfigParser.InterpolationError

Base class for exceptions raised when problems occur performing string interpolation.

exception ConfigParser.InterpolationDepthError

Exception raised when string interpolation cannot be completed because the number of iterations exceeds MAX_INTERPOLATION_DEPTH. Subclass of InterpolationError.

exception ConfigParser.InterpolationMissingOptionError

Exception raised when an option referenced from a value does not exist. Subclass of InterpolationError.

New in version 2.3.

exception ConfigParser.InterpolationSyntaxError

Exception raised when the source text into which substitutions are made does not conform to the required syntax. Subclass of InterpolationError.

New in version 2.3.

exception ConfigParser.MissingSectionHeaderError

Exception raised when attempting to parse a file which has no section headers.

exception ConfigParser.ParsingError

Exception raised when errors occur attempting to parse a file.

ConfigParser.MAX_INTERPOLATION_DEPTH

The maximum depth for recursive interpolation for get() when the raw parameter is false. This is relevant only for the ConfigParser class.

See also

Module shlex

Support for a creating Unix shell-like mini-languages which can be used as an alternate format for application configuration files.

13.2.1. RawConfigParser Objects

RawConfigParser instances have the following methods:

RawConfigParser.defaults()

Return a dictionary containing the instance-wide defaults.

RawConfigParser.sections()

Return a list of the sections available; DEFAULT is not included in the list.

RawConfigParser.add_section(section)

Add a section named section to the instance. If a section by the given name already exists, DuplicateSectionError is raised. If the name DEFAULT (or any of it’s case-insensitive variants) is passed, ValueError is raised.

RawConfigParser.has_section(section)

Indicates whether the named section is present in the configuration. The DEFAULT section is not acknowledged.

RawConfigParser.options(section)

Returns a list of options available in the specified section.

RawConfigParser.has_option(section, option)

If the given section exists, and contains the given option, return True; otherwise return False.

New in version 1.6.

RawConfigParser.read(filenames)

Attempt to read and parse a list of filenames, returning a list of filenames which were successfully parsed. If filenames is a string or Unicode 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')])

Changed in version 2.4: Returns list of successfully parsed filenames.

RawConfigParser.readfp(fp[, filename])

Read and parse configuration data from the file or file-like object in fp (only the readline() method is used). If filename is omitted and fp has a name attribute, that is used for filename; the default is <???>.

RawConfigParser.get(section, option)

Get an option value for the named section.

RawConfigParser.getint(section, option)

A convenience method which coerces the option in the specified section to an integer.

RawConfigParser.getfloat(section, option)

A convenience method which coerces the option in the specified section to a floating point number.

RawConfigParser.getboolean(section, option)

A convenience method which coerces the option in the specified section to a Boolean value. Note that the accepted values for the option are "1", "yes", "true", and "on", which cause this method to return True, and "0", "no", "false", and "off", which cause it to return False. These string values are checked in a case-insensitive manner. Any other value will cause it to raise ValueError.

RawConfigParser.items(section)

Return a list of (name, value) pairs for each option in the given section.

RawConfigParser.set(section, option, value)

If the given section exists, set the given option to the specified value; otherwise raise NoSectionError. While it is possible to use RawConfigParser (or ConfigParser with raw parameters set to true) for internal storage of non-string values, full functionality (including interpolation and output to files) can only be achieved using string values.

New in version 1.6.

RawConfigParser.write(fileobject)

Write a representation of the configuration to the specified file object. This representation can be parsed by a future read() call.

New in version 1.6.

RawConfigParser.remove_option(section, option)

Remove the specified option from the specified section. If the section does not exist, raise NoSectionError. If the option existed to be removed, return True; otherwise return False.

New in version 1.6.

RawConfigParser.remove_section(section)

Remove the specified section from the configuration. If the section in fact existed, return True. Otherwise return False.

RawConfigParser.optionxform(option)

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.

13.2.2. ConfigParser Objects

The ConfigParser class extends some methods of the RawConfigParser interface, adding some optional arguments.

ConfigParser.get(section, option[, raw[, vars]])

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.

ConfigParser.items(section[, raw[, vars]])

Return a list of (name, value) pairs for each option in the given section. Optional arguments have the same meaning as for the get() method.

New in version 2.3.

13.2.3. SafeConfigParser Objects

The SafeConfigParser class implements the same extended interface as ConfigParser, with the following addition:

SafeConfigParser.set(section, option, value)

If the given section exists, set the given option to the specified value; otherwise raise NoSectionError. value must be a string (str or unicode); if not, TypeError is raised.

New in version 2.4.

13.2.4. Examples

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', 'an_int', '15')
config.set('Section1', 'a_bool', 'true')
config.set('Section1', 'a_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
a_float = config.getfloat('Section1', 'a_float')
an_int = config.getint('Section1', 'an_int')
print a_float + an_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', 'a_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)

Some configuration files are known to include settings without values, but which otherwise conform to the syntax supported by ConfigParser. The allow_no_value parameter to the constructor can be used to indicate that such values should be accepted:

>>> import ConfigParser
>>> import io

>>> sample_config = """
... [mysqld]
... user = mysql
... pid-file = /var/run/mysqld/mysqld.pid
... skip-external-locking
... old_passwords = 1
... skip-bdb
... skip-innodb
... """
>>> config = ConfigParser.RawConfigParser(allow_no_value=True)
>>> config.readfp(io.BytesIO(sample_config))

>>> # Settings with values are treated as before:
>>> config.get("mysqld", "user")
'mysql'

>>> # Settings without values provide None:
>>> config.get("mysqld", "skip-bdb")

>>> # Settings which aren't specified still raise an error:
>>> config.get("mysqld", "does-not-exist")
Traceback (most recent call last):
  ...
ConfigParser.NoOptionError: No option 'does-not-exist' in section: 'mysqld'