llvm-project/lldb/examples/summaries/cocoa/attrib_fromdict.py

"""
Objective-C runtime wrapper for use by LLDB Python formatters

part of The LLVM Compiler Infrastructure
This file is distributed under the University of Illinois Open Source
License. See LICENSE.TXT for details.
"""
class AttributesDictionary:
	def __init__(self, allow_reset = True):
		self.__dict__['_dictionary'] = {} # need to do it this way to prevent endless recursion
		self.__dict__['_allow_reset'] = allow_reset

	def __getattr__(self,name):
		if not self._check_exists(name):
			return None
		value = self._dictionary[name]
		return value

	def _set_impl(self,name,value):
		self._dictionary[name] = value

	def _check_exists(self,name):
		return name in self._dictionary

	def __setattr__(self,name,value):
		if self._allow_reset:
			self._set_impl(name,value)
		else:
			self.set_if_necessary(name,value)

	def set_if_necessary(self,name,value):
		if not self._check_exists(name):
			self._set_impl(name,value)
			return True
		return False

	def __len__(self):
		return len(self._dictionary)