python - nosetest error: ValueError: dictionary update sequence element #0 has length 4; 2 is required -

i noob , w/r/t python 2.7 , exercise i'm working through on learn python hard way (link ex47) - file below named ex47_tests.py , error related running nosetests directory i'm working in.

according nosetests, error test_map() function @ line west.add_paths({'east', start}) , states: valueerror: dictionary update sequence @ element #0 has length 4; 2 required cannot understand problem is... here's test file:

from nose.tools import * ex47.game import room   def test_room():     gold = room("goldroom",                  """this room has gold in can grab. there's                 door north.""")     assert_equal(gold.name, "goldroom")     assert_equal(gold.paths, {})  def test_room_paths():     center = room("center", "test room in center.")     north = room("north", "test room in north.")     south = room("south", "test room in south.")      center.add_paths({'north': north, 'south':south})     assert_equal(center.go('north'), north)     assert_equal(center.go('south'), south)  def test_map():     start = room("start", "you can go west , down hole.")     west = room("trees", "there trees here, can go east.")     down = room("dungeon", "it's dark down here, can go up.")      start.add_paths({'west': west, 'down': down})     west.add_paths({'east', start})     down.add_paths({'up': start})      assert_equal(start.go('west'), west)     assert_equal(start.go('west').go('east'), start)     assert_equal(start.go('down').go('up'), start) 

for reference, game.py file contains room class has add_paths function (method?):

class room(object):      def __init__(self, name, description):         self.name = name         self.description = description         self.paths = {}      def go(self, direction):         return self.paths.get(direction, none)      def add_paths(self, paths):         self.paths.update(paths) 

i've reviewed several times , have run code west.add_paths({'east', start}) within game.py file when run nosetestsi keep getting same error. @ point in code error occurs, interpretation west contains empty {} should update without issue, no? can provide insight why isn't working , error comes from?

thank much.

the bug in code coming call:

west.add_paths({'east', start}) 

the correction made this, want update dictionary, not set:

west.add_paths({'east': start}) 

this error reproducible following example when try update dictionary set:

>>> d = {} >>> d.update({'east','start'}) traceback (most recent call last):   file "<stdin>", line 1, in <module> valueerror: dictionary update sequence element #0 has length 5; 2 required 

to provide more clarity on bug, if go interpreter , check type of this:

notice comma between 'east' , 'start'

>>> print(type({'east', 'start'})) <type 'set'> 

notice colon between 'east' , 'start'

>>> print(type({'east': 'start'})) <type 'dict'>