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  1. from itertools import chain, groupby
  2.  
  3. def group2_jfs(iterable, isstart):
  4.     # ABNF Grammar:# iterable = [ body ] *( header [ body ] )
  5.     it = groupby(iterable, isstart)
  6.  
  7.     # [ body ]
  8.     start, headers_or_body = next(it)
  9.     if not start:  # body
  10.         yield headers_or_body
  11.         start, headers = next(it)
  12.     else:  # 1*header
  13.         headers = headers_or_body
  14.  
  15.     while True:  # 1*( header [ body ] )
  16.         assert start
  17.         bodyless_header = None
  18.         for header in headers:  # yield all but last header
  19.             if bodyless_header is not None:
  20.                 yield iter([bodyless_header])
  21.             bodyless_header = header
  22.  
  23.         try:
  24.             start, body = next(it)
  25.         except StopIteration:
  26.             yield iter([header])  # the last header is bodyless
  27.             break
  28.         else:
  29.             assert not start
  30.             assert header is not None
  31.             yield chain([header], body)
  32.         start, headers = next(it)
  33.  
  34. from collections import deque
  35.  
  36. deque(group2_jfs(range(10**7), lambda x: x % 1000 == 0), maxlen=0)
  37.  
Success #stdin #stdout 6.99s 5744KB
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https://ideone.com/emXYf
language:
Python 3 (python  3.12)
created:
13 years ago
visibility:
secret

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