Python AMKA Validator (no string slice)

gistfile1.py

def ValidateAMKA (amka):
  if len(amka) != 11 or amka.isdigit() == False:
		return False
	else:
		sum = int(amka[10])
		i = 0		
		for s in amka[0:10]:
			if i%2 != 0:
				if int(s)* 2 > 9:
					sum += int(s)*2 % 10+1
				else:
					sum += int(s)* 2
			else:
				sum += int(s)
			i = i + 1
		if sum%10 == 0:

			return True
		else:
			return False