How to use tuples as parameters for __getitem__()?

Question

I'm writing a custom class that wraps a dict. As such, I want to implement getitem for it. I also will be using tuples as keys in this dict. However, when I try to pass a tuple to getitem, Python throws a KeyError. It looks like it's casting my tuple to an int when I pass it to getitem :

Code:

Class Board(object):
  def __getitem__(self, key):
    print "type in call: " + type(key)
    return self.board[key]

# in main somewhere
board = Board()

print "type before call: " + type((1, 2))
if (1, 2) in board:
  print "It's there!"

Ouptut:

type before call: <type 'tuple'>
type in call: <type 'int'>

## traceback stuff ##
KeyError: 0

Does Board need to inherit from a mapping type for Python to be happy? Also, why does Python try to do this cast in the first place?

Answer 1

Containment iterates unless __contains__() is implemented. So, implement it.