Help with Singleton SafeConfigParser
Peter Otten
__peter__ at web.de
Sat Dec 8 12:40:07 EST 2012
Josh English wrote:
> I have seen older posts in this group that talk about using modules as
singletons, but this, unless I misunderstand, requires me to code the entire
API for SafeConfigParser in the module:
>
> <pre>
> import ConfigParser
>
>
> class Options(ConfigParser.SafeConfigParser):
> def __init__(self):
> ConfigParser.SafeConfigParser.__init__(self)
> self.readfp(open('defaults.cfg'))
> self.read(['local.txt', 'local.cfg'])
>
> def save(self):
> with open('local.txt','w') as f:
> self.write(f)
>
> __options = Options()
>
> def set(section, name, value):
> return self.__options.set(section, name, value)
>
> def options(section):
> return self.__options.options
>
> # And so on
> </pre>
>
> This seems incredibly wasteful, and to introspect my options I get a
module, not a SafeConfigParser object, so I'm wondering if there is a
different way to handle this?
Two underscores trigger name mangling only in a class, not in a module.
Don't try to hide the Options instance:
# module config.py
import ConfigParser
class Options(ConfigParser.SafeConfigParser):
... # as above
options = Options()
Then use it elsewhere:
from config import options
options.set("mysection", "myoption", "myvalue")
All but the first import will find the module in the cache (sys.modules) and
therefore the same Options instance will be used. Voilà your no-nonsense
singleton.
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