def __init__( self, schema=None, fname=None ):
		'''schema -> 'field1:atype field2:atype ...' where atype is a
			python array type code (see eg below)'''
		if fname:
			self.load( fname )
		else:
			if type(schema) == str:
				schema = [ f.split(':') for f in schema.split() ]
			self.schema = schema
			self.flist = [ f for f,t in schema ]
			self.data = dict( [(f, array.array(t)) for f,t in schema] )
			self.rowcount = 0
schema -> 'field1:atype field2:atype ...' where atype is a
			python array type code (see eg below)
recipes/Python/577698_Simple_numeric_database/recipe-577698.py