class EngineeringNumberConverter():

	prefixes = [
		('y', 1e-24),
		('z', 1e-21),
		('a', 1e-18),
		('f', 1e-15),
		('p', 1e-12),
		('n', 1e-9),
		('u', 1e-6),
		('m', 1e-3),
		# We skip centi and dezi because no one really uses these besides for length measurements
		('', 1),
		# We also skip h for hekto
		('k', 1e3),
		('M', 1e6),
		('G', 1e9),
		('T', 1e12),
		('P', 1e15),
		('E', 1e18),
		('Z', 1e21),
		('Y', 1e24),
	]
	it_prefixes = [
		('', 1),
		('Ki', 1024),
		('Mi', 1024*1024),
		('Gi', 1024*1024*1024),
		('Ti', 1024*1024*1024*1024)
	]

	@classmethod
	def number_to_engineering(c, number, it_unit=False):
		"""
		Convert a number to engineering SI syntax with prefix.
		This function will return a tuple of (new_number, prefix)
		"""
		if it_unit:
			used_prefixes = c.it_prefixes
		else:
			used_prefixes = c.prefixes

		if (len(used_prefixes) < 2):
			return (number / used_prefixes[0][1], used_prefixes[0])

		for i, (prefix, scale) in enumerate(used_prefixes[1:], 1):
			if number < scale:
				return (number / used_prefixes[i-1][1], used_prefixes[i-1][0])

		return (number / used_prefixes[-1][1], used_prefixes[-1][0])

	@classmethod
	def engineering_to_number(c, input):
		cleaned_input = input.strip().replace(' ', '')

		selected_scaling = 1

		for (prefix, scale) in c.prefixes+c.it_prefixes:
			if prefix == '':
				continue
			if cleaned_input.endswith(prefix):
				cleaned_input = cleaned_input.replace(prefix, '')
				selected_scaling = scale
				break

		return float(cleaned_input) * selected_scaling