def ternary (n):
if n == 0:
return '0'
nums = []
while n:
n, r = divmod(n, 3)
nums.append(str(r))
return ''.join(reversed(nums))
>>> ternary(0)
'0'
>>> ternary(1)
'1'
>>> ternary(2)
'2'
>>> ternary(3)
'10'
>>> ternary(12)
'110'
>>> ternary(22)
'211'