A Dictionary of Links

I wanted a dictionary of links for an MD type simulation, and I wanted the links to be unique, and I didn't want to have to check for the order the guys appeared in the dictionary keys every time, so I wrote my own dictionary by extending the native one.

	class Links(dict):
	""" An extended dictionary class
	that handles tuple keys nicely,
	by ordering the tuple calls """
	def __init__(self,info=None,**kwargs):
	super(Links,self).__init__()
	if info:
	if hasattr(info,'iteritems'):
	for key,value in info.iteritems():
	self.__setitem__(key,value)
	elif iterable(info):
	for key,value in info:
	self.__setitem__(key,value)
	for key,value in kwargs.iteritems():
	self.__setitem__(key,value)
	def order_first_tuple(func):
	def orderedversion(self,first,*args,**kwargs):
	assert hasattr(first,"__len__"), "Key must be iterable"
	assert len(first)==2, "Key must be 2-tuple"
	ordered_first = tuple(sorted(first))
	return func(self,ordered_first,*args,**kwargs)
	return orderedversion
	@order_first_tuple
	def __setitem__(self,key,val):
	return super(Links,self).__setitem__(key,val)
	@order_first_tuple
	def __getitem__(self,*args):
	return super(Links,self).__getitem__(*args)
	@order_first_tuple
	def __delitem__(self,*args):
	return super(Links,self).__delitem__(*args)
	@order_first_tuple
	def __contains__(self,*args):
	return super(Links,self).__contains__(*args)

view raw links.py hosted with ❤ by GitHub

Where I put that code on gist. To pull it off, you see that I subclass dict, and define a decorator that pulls out and sorts the first argument. After that it is just decorating the '__setitem__','__getitem__',and '__delitem__' methods. This lets us do nice things now:

>>> z = Links()
>>> z[1,2] = 5
>>> z[4,3] = 10
>>> z
{(1, 2): 5, (3, 4): 10}
>>> z[2,1]
5
>>> z[1,2]
5
>>> z[2,1] = 11
>>> z
{(1, 2): 11, (3, 4): 10}
>>> del z[2,1]
>>> (3,4) in z
True
>>> (4,3) in z
True
>>> z
{(3, 4): 10}
>>> z[5] = 1
Traceback (most recent call last):
  File "", line 1, in 
  File "links.py", line 10, in orderedversion
    assert hasattr(first,"__len__"), "Key must be iterable"
AssertionError: Key must be iterable
>>> z[4,4,3] = 1
Traceback (most recent call last):
  File "", line 1, in 
  File "links.py", line 11, in orderedversion
    assert len(first)==2, "Key must be 2-tuple"
AssertionError: Key must be 2-tuple
>>> z
{(3, 4): 10}