RosettaCodeData/Task/Look-and-say-sequence/Python/look-and-say-sequence-3.py

>>> from itertools import groupby, islice
>>>
>>> def lookandsay(number='1'):
  while True:
    yield number
    number = ''.join( str(len(list(g))) + k
                      for k,g in groupby(number) )


>>> print('\n'.join(islice(lookandsay(), 10)))
1
11
21
1211
111221
312211
13112221
1113213211
31131211131221
13211311123113112211