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  1. from itertools import islice, zip_longest
  2. import string
  3. from typing import Iterator, Sequence
  4.  
  5.  
  6. def sliding_window_of[T](window_length: int, iterable: Sequence[T]) -> Iterator[tuple[T, *tuple[T | None, ...]]]:
  7.     assert window_length >= 1
  8.     window_its = [
  9.         islice(iterable, i, None, None)
  10.         for i in range(window_length)
  11.     ]
  12.     yield from zip_longest(*window_its)  # type:ignore
  13.  
  14.  
  15. def get_opts(options: str) -> list[str]:
  16.     # validations
  17.     if not all(opt == '/' or opt in string.ascii_lowercase for opt in options):
  18.         raise ValueError("options string must be only lowercase letters or slashes")
  19.  
  20.     if options.startswith('/') or options.endswith('/'):
  21.         raise ValueError("must not start of end with a slash")
  22.  
  23.     if any(window == ('/', '/') for window in sliding_window_of(2, options)):
  24.         raise ValueError("a slash cannot be followed by another slash")
  25.  
  26.     triples = sliding_window_of(3, options)
  27.     opts = list[str]()
  28.  
  29.     # first case is special because we need to get the left-most character
  30.     match next(triples, None):
  31.         case (a, '/', str(b)):
  32.             opts.append(a+b)
  33.         case (a, _, '/'):
  34.             opts.append(a)
  35.         case (a, str(b), _):
  36.             opts.extend((a, b))
  37.  
  38.     for triple in triples:
  39.         match triple:
  40.             case ('/', _, _) | (_, _, '/'):
  41.                 pass
  42.             case (a, '/', str(b)):
  43.                 opts.append(a+b)
  44.             case (_, str(a), _):
  45.                 opts.append(a)
  46.  
  47.     return opts
  48.  
  49.  
  50. for opts in ["abcd/efgh/ijk", "abc//def", "invalid!chars", "/a", "b/"]:
  51.     try:
  52.         print(f"{opts} => {get_opts(opts)}")
  53.     except ValueError as ve:
  54.         print(f"{opts} => {ve!r}")
  55.  
Success #stdin #stdout 0.25s 17292KB
comments (?)
stdin 
Standard input is empty
stdout 
abcd/efgh/ijk => ['a', 'b', 'c', 'de', 'f', 'g', 'hi', 'j', 'k']
abc//def => ValueError('a slash cannot be followed by another slash')
invalid!chars => ValueError('options string must be only lowercase letters or slashes')
/a => ValueError('must not start of end with a slash')
b/ => ValueError('must not start of end with a slash')
https://ideone.com/C3alFz
language:
Python 3 (python  3.12)
created:
13 days ago
visibility:
public

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