implement combo config parser

allows all options to be overridden by command line.

e.g.
[watchd]
threads=10
debug=false

--watch.threads=50 --debug=true

comboparse.py

@@ -0,0 +1,86 @@
+from ConfigParser import SafeConfigParser, NoOptionError
+from argparse import ArgumentParser
+import sys
+
+class _Dummy():
+	pass
+
+class ComboParser(object):
+	def __init__(self, ini):
+		self.items = []
+		self.cparser = SafeConfigParser()
+		self.aparser = ArgumentParser()
+		self.ini = ini
+		self.items = []
+		self.loaded = False
+
+	def add_item(self, section, name, type, default, desc, required):
+		self.items.append({
+			'section':section,
+			'name':name,
+			'type':type,
+			'default':default,
+			'required':required,
+		})
+		self.aparser.add_argument(
+			'--%s.%s'%(section, name),
+			help='%s, default: (%s)'%(desc, str(default)),
+			type=type,
+			default=None,
+			required=False
+		)
+	def load(self):
+		if self.loaded: return
+		self.loaded = True
+
+		try: self.cparser.read(self.ini)
+		except: pass
+		args = self.aparser.parse_args()
+		for item in self.items:
+			try:
+				obj = getattr(self, item['section'])
+			except AttributeError:
+				setattr(self, item['section'], _Dummy())
+				obj = getattr(self, item['section'])
+
+			setattr(obj, item['name'], item['default'])
+			inner = getattr(obj, item['name'])
+
+			item['found'] = True
+			try:
+				if   item['type'] is bool : inner = self.cparser.getboolean(item['section'], item['name'])
+				elif item['type'] is float: inner = self.cparser.getfloat(item['section'], item['name'])
+				elif item['type'] is int  : inner = self.cparser.getint(item['section'], item['name'])
+				elif item['type'] is str  : inner = self.cparser.get(item['section'], item['name'])
+			except NoOptionError:
+				item['found'] = False
+			try:
+				arg = getattr(args, '%s.%s'%(item['section'], item['name']))
+				if arg is not None:
+					inner = arg
+					item['found'] = True
+			except: pass
+			if not item['found']:
+				if item['required']:
+					sys.stderr.write('error: required config item "%s" not found in section "%s" of "%s"!\n'%(item['name'], item['section'], self.ini))
+					sys.exit(1)
+				else:
+					sys.stderr.write('warning: assigned default value of "%s" to "%s.%s"\n'%(str(item['default']), item['section'], item['name']))
+			setattr(obj, item['name'], inner)
+
+
+# TEST CODE
+def _main():
+	config = ComboParser('config.ini')
+	config.add_item('watchd', 'debug', bool, False, 'turn additional debug info on', False)
+	config.add_item('watchd', 'float', float, 0.1, 'a float test', True)
+	config.add_item('watchd', 'strupp', str, "sup", 'a str test', False)
+	config.add_item('common', 'tor_host', str, '127.0.0.1:9050', 'address of tor proxy', True)
+	config.load()
+	print config.watchd.debug
+	print config.watchd.float
+	print config.watchd.strupp
+	print config.common.tor_host
+
+if __name__ == '__main__':
+	_main()