def split(slicable, fraction):
	"""
	splits data into test-train set or dev-validation set; does not shuffle.

	params: slicable - an object that responds to len() and [], works on dataframes
	        fraction - a value between 0 and 1
	returns: (x, y) - where x has (1-fraction) percent entries and y has the rest
	"""
	partition = int(len(slicable) * (1.0 - fraction));
	return( (slicable[:partition], slicable[partition:]) );