init-once class 'static' data

[George Young]

I seem to often need a class to initialize a piece of it's data
the first time that class is instantiated.  Examples might be a database
connection, a loading a pixmap, loading and parsing a datafile which
data will normally be accessed as a directory member of the class...

I'd rather the data not initialize on module load, because in some cases
the data may never be used.

I've been using an idiom I copied once from someone, but it seems
pretty kludgy, I'm hoping someone will point out a better way:

class foo:
	data = None
	def __init__(self, data=data):
		if data:
			self.data = data
		else:
			self.data = (some expensive operation)

-- George

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