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  1. # An attempt to emulate scope guard statements of the D Programming Language
  2. # see: http://d...content-available-to-author-only...s.com/2.0/statement.html#ScopeGuardStatement
  3.  
  4. def noop(*args, **kwargs):
  5.     pass
  6.  
  7. def mkCbAdder(typ):
  8.     def adder(self, cb):
  9.         self.callbacks.append( (typ, cb) )
  10.     return adder
  11.  
  12. class Scope(object):
  13.  
  14.     def __init__(self):
  15.         self.callbacks = []
  16.  
  17.     exit = property(noop, mkCbAdder('exit'))
  18.     success = property(noop, mkCbAdder('ok'))
  19.     failure = property(noop, mkCbAdder('fail'))
  20.  
  21.     def __enter__(self):
  22.         return self
  23.  
  24.     def __exit__(self, type, value, traceback):
  25.         ok = value is None
  26.         while self.callbacks:
  27.             typ, cb = self.callbacks.pop()
  28.             if typ is 'exit':
  29.                 cb()
  30.             elif ok and typ is 'ok':
  31.                 cb()
  32.             elif not ok and (typ is 'fail'):
  33.                 cb()
  34.  
  35.  
  36. def write(arg):
  37.     return lambda: print(arg, end="")
  38.  
  39.  
  40. write(1)()
  41. with Scope() as s:
  42.     write(2)()
  43.     s.exit = write(3)
  44.     s.exit = write(4)
  45.     write(5)()
  46.  
  47. # 12543
  48.  
  49. print()
  50.  
  51. with Scope() as s:
  52.     s.exit = write(1)
  53.     s.success = write(2)
  54.     s.exit = write(3)
  55.     s.success = write(4)
  56.  
  57. # 4321
  58.  
  59. print()
  60.  
  61. try:
  62.     with Scope() as s:
  63.         s.exit = write(1)
  64.         s.success = write(2)
  65.         s.failure = write(3)
  66.         raise Exception("msg")
  67.         s.exit = write(4)
  68.         s.success = write(5)
  69.         s.failure = write(6)
  70.  
  71. except Exception as e:
  72.     pass
  73.  
  74. # 31
  75.  
Success #stdin #stdout 0.02s 5908KB
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12543
4321
31
https://ideone.com/vNmq8
language:
Python 3 (python  3.9.5)
created:
12 years ago
visibility:
public

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