odslicer.py

from collections import OrderedDict
from collections.abc import Iterable

class ModOD(OrderedDict):
	def __repr__(self):
		if not len(self):
			return 'od()'
		return 'od[' + ', '.join('{}: {}'.format(k, v) for k, v in self.items()) + ']'

od_syntax_error = SyntaxError('Allowed sytax: od[<k>: <v>(, <k>: <v>, …)] or od()')

class ODSlicer:
	def __call__(self):
		return ModOD()
	
	def __getitem__(self, keys):
		if isinstance(keys, slice):
			keys = [keys]
		
		if not isinstance(keys, Iterable):
			raise od_syntax_error
		
		d = ModOD()
		
		for key in keys:
			if not isinstance(key, slice) or key.step is not None:
				raise od_syntax_error
			
			d[key.start] = key.stop
		
		return d

od = ODSlicer()