Python subroutine that returns hard disk serial no

get_serial.py

def get_serial():
	# TODO: find where root is mounted (mmcblk1p2), get mmcblk1 by cutting off
	#  2-byte tail
	f = '/sys/block/mmcblk1/device/serial'
	if os.path.isfile(f):
		with open(f, 'rb') as i:
			n = i.read().rstrip()
		if n[:2] == b'0x':
			n = n[2:]
		return n
	f = '/sys/block/sda/device/vpd_pg80'
	if os.path.isfile(f):
		with open(f, 'rb') as i:
			n = i.read().rstrip()
		n=n[4:]
		return n