import pysnooper
@pysnooper.snoop()
def number_to_bits(number):
  if number:
    bits = []
    while number:
      number, remainder = divmod(number, 2)
      bits.insert(0, remainder)
    return bits
  else:
    return [0]
number_to_bits(6)

Starting var:.. number = 6
21:14:32.099769 call     3 @pysnooper.snoop()
21:14:32.099769 line     5   if number:
21:14:32.099769 line     6     bits = []
New var:....... bits = []
21:14:32.099769 line     7     while number:
21:14:32.099769 line     8       number, remainder = divmod(number, 2)
New var:....... remainder = 0
Modified var:.. number = 3
21:14:32.099769 line     9       bits.insert(0, remainder)
Modified var:.. bits = [0]
21:14:32.099769 line     7     while number:
21:14:32.099769 line     8       number, remainder = divmod(number, 2)
Modified var:.. number = 1
Modified var:.. remainder = 1
21:14:32.099769 line     9       bits.insert(0, remainder)
Modified var:.. bits = [1, 0]
21:14:32.099769 line     7     while number:
21:14:32.099769 line     8       number, remainder = divmod(number, 2)
Modified var:.. number = 0
21:14:32.099769 line     9       bits.insert(0, remainder)
Modified var:.. bits = [1, 1, 0]
21:14:32.099769 line     7     while number:
21:14:32.099769 line    10     return bits
21:14:32.099769 return   10     return bits