nDimensional sparse histogram in python.

[KraftDiner]

Ok so this is nice.. Just one thing.. When you try to get a value from
a dictionary
and it isn't found in the dictionary things go bad...

Take this for example:

class histogram(object):
	def __init__(self):
		self.histo = {}

	def update(self, point):
		if self.histo.get(point) != None:
			self.histo[point] = self.histo[point] + 1
		else:
			self.histo[point] = 1

	def get(self, point):
		return self.histo[point]


hist = histogram()
hist.update((0,0,0))
hist.update((0,0,1))
hist.update((0,0,1))
hist.get((0,0,0))
hist.get((0,0,1))
hist.get((0,0,2))

spews out this error:

Traceback (most recent call last):
  File "histogram.py", line 21, in ?
    hist.get((0,0,2))
  File "histogram.py", line 12, in get
    return self.histo[point]
KeyError: (0, 0, 2)