Number Conversions in Python

def Den2Bin(den):
  bin = ""
  while den > 0:
    rem = den % 2
    bin = str(rem) + bin
    den //= 2
  return bin

def Bin2Den(bin):
  exp, oct = 0, 0
  bin = str(bin)
  for i in bin[::-1]:
    i = int(i)
    raised = i * (2 ** exp)
    oct += raised
    exp += 1
  return oct

print(Den2Bin(28))
print(Bin2Den(1010))