python configparser中默认值的设定方式

try:
    apple = config.get(section, 'apple')
except NoSectionError, NoOptionError:
    apple = None

class DefaultOption(dict):
    def __init__(self, config, section, **kv):
        self._config = config
        self._section = section
        dict.__init__(self, **kv)
    def items(self):
        _items = []
        for option in self:
            if not self._config.has_option(self._section, option):
                _items.append((option, self[option]))
            else:
                value_in_config = self._config.get(self._section, option)
                _items.append((option, value_in_config))
        return _items

def read_config(section, location):
    config = configparser.ConfigParser()
    config.read(location)
    apple = config.get(section, 'apple',
                       vars=DefaultOption(config, section, apple=None))
    pear = config.get(section, 'pear',
                      vars=DefaultOption(config, section, pear=None))
    banana = config.get(section, 'banana',
                        vars=DefaultOption(config, section, banana=None))
    return apple, pear, banana

[DEFAULT]
ServerAliveInterval = 45
Compression = yes
CompressionLevel = 9
ForwardX11 = yes
[bitbucket.org]
User = hg
[topsecret.server.com]
Port = 50022
ForwardX11 = no

>> import configparser
>>> config = configparser.ConfigParser()
>>> config.sections()
[]
>>> config.read('example.ini')
['example.ini']
>>> config.sections()
['bitbucket.org', 'topsecret.server.com']
>>> 'bitbucket.org' in config
True
>>> 'bytebong.com' in config
False
>>> config['bitbucket.org']['User']
'hg'
>>> config['DEFAULT']['Compression']
'yes'
>>> topsecret = config['topsecret.server.com']
>>> topsecret['ForwardX11']
'no'
>>> topsecret['Port']
'50022'
>>> for key in config['bitbucket.org']: print(key)
...
user
compressionlevel
serveraliveinterval
compression
forwardx11
>>> config['bitbucket.org']['ForwardX11']
'yes'

[Simple Values]
key=value
spaces in keys=allowed
spaces in values=allowed as well
spaces around the delimiter = obviously
you can also use : to delimit keys from values
[All Values Are Strings]
values like this: 1000000
or this: 3.14159265359
are they treated as numbers? : no
integers, floats and booleans are held as: strings
can use the API to get converted values directly: true
[Multiline Values]
chorus: I'm a lumberjack, and I'm okay
    I sleep all night and I work all day
[No Values]
key_without_value
empty string value here =
[You can use comments]
# like this
; or this
# By default only in an empty line.
# Inline comments can be harmful because they prevent users
# from using the delimiting characters as parts of values.
# That being said, this can be customized.
    [Sections Can Be Indented]
        can_values_be_as_well = True
        does_that_mean_anything_special = False
        purpose = formatting for readability
        multiline_values = are
            handled just fine as
            long as they are indented
            deeper than the first line
            of a value
        # Did I mention we can indent comments, too?

config.write(open（'example.ini', 'w'）)

with open('example.ini', 'w') as configfile:
    config.write(configfile)