>>> def g(stream):
...     state = 'wait_digit'
...     accumulator = ''
...     while True:
...         ch = stream.read(1)
...         if not ch:
...             break
...         if state == 'wait_digit':
...             if ch.isdigit():
...                 accumulator += ch
...                 state = 'wait_nondigit'
...         elif state == 'wait_nondigit':
...             if ch.isdigit():
...                 accumulator += ch
...             else:
...                 number = int(accumulator)
...                 accumulator = ''
...                 yield number
...                 state = 'wait_digit'
... 
>>> 
>>> import sys            
>>> 
>>> numbers = g(sys.stdin)
>>> 
>>> next(numbers)         
  111  222  333  x  444
111
>>> next(numbers)
222
>>> next(numbers)
333
>>> next(numbers)
444
>>> next(numbers)
555
555
>>> next(numbers)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>> 
>>> 
>>> import io
>>> 
>>> numbers = g(io.StringIO('  11  22  33 x 44 x 55  '))
>>> 
>>> next(numbers)
11
>>> next(numbers)
22
>>> next(numbers)
33
>>> next(numbers)
44
>>> next(numbers)
55
>>> next(numbers)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>>