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  1. import gc
  2. import types
  3. import inspect
  4. from typing import Optional
  5. from weakref import WeakKeyDictionary
  6.  
  7. def proxy0(data):
  8.     def proxy1(): return data
  9.     return proxy1
  10.  
  11. _CELLTYPE = type(proxy0(None).__closure__[0])
  12.  
  13. def replace_all_refs(org_obj, new_obj):
  14.     gc.collect()
  15.  
  16.     hit = False
  17.     for referrer in gc.get_referrers(org_obj):
  18.         if isinstance(referrer, types.FrameType):
  19.             continue
  20.         if isinstance(referrer, dict):
  21.             cls = None
  22.             if '__dict__' in referrer and '__weakref__' in referrer:
  23.                 for cls in gc.get_referrers(referrer):
  24.                     if inspect.isclass(cls) and cls.__dict__ == referrer:
  25.                         break
  26.             for key, value in referrer.items():
  27.                 if value is org_obj:
  28.                     hit = True
  29.                     value = new_obj
  30.                     referrer[key] = value
  31.                     if cls:
  32.                         setattr(cls, key, new_obj)
  33.                 if key is org_obj:
  34.                     hit = True
  35.                     del referrer[key]
  36.                     referrer[new_obj] = value
  37.         elif isinstance(referrer, list):
  38.             for i, value in enumerate(referrer):
  39.                 if value is org_obj:
  40.                     hit = True
  41.                     referrer[i] = new_obj
  42.         elif isinstance(referrer, set):
  43.             referrer.remove(org_obj)
  44.             referrer.add(new_obj)
  45.             hit = True
  46.         elif isinstance(referrer, (tuple, frozenset,)):
  47.             new_tuple = []
  48.             for obj in referrer:
  49.                 if obj is org_obj:
  50.                     new_tuple.append(new_obj)
  51.                 else:
  52.                     new_tuple.append(obj)
  53.             replace_all_refs(referrer, type(referrer)(new_tuple))
  54.         elif isinstance(referrer, _CELLTYPE):
  55.             def proxy0(data):
  56.                 def proxy1(): return data
  57.                 return proxy1
  58.             proxy = proxy0(new_obj)
  59.             newcell = proxy.__closure__[0]
  60.             replace_all_refs(referrer, newcell)
  61.         elif isinstance(referrer, types.FunctionType):
  62.             localsmap = {}
  63.             for key in ['__code__', '__globals__', '__name__',
  64.                         '__defaults__', '__closure__']:
  65.                 orgattr = getattr(referrer, key)
  66.                 if orgattr is org_obj:
  67.                     localsmap[key[2:-2]] = new_obj
  68.                 else:
  69.                     localsmap[key[2:-2]] = orgattr
  70.             localsmap['argdefs'] = localsmap['defaults']
  71.             del localsmap['defaults']
  72.             newfn = types.FunctionType(**localsmap)
  73.             replace_all_refs(referrer, newfn)
  74.     if hit is False:
  75.         raise AttributeError("Object '%r' not found" % org_obj)
  76.     return org_obj
  77.  
  78. class DeferredStrProperty:
  79.     instances = WeakKeyDictionary()
  80.  
  81.     def __init__(self, attribute):
  82.         self.attribute = attribute
  83.  
  84.     def __get__(self, obj, objtype=None):
  85.         if obj is None:
  86.             return vars(objtype)[self.attribute]
  87.         if (deferred_str := self.instances.get(obj)) is None:
  88.             return vars(obj)[self.attribute]
  89.         return deferred_str
  90.  
  91.     def __set__(self, obj, value):
  92.         if (deferred_str := self.instances.get(obj)) is None:
  93.             vars(obj)[self.attribute] = value
  94.         else:
  95.             replace_all_refs(deferred_str, value)
  96.             del self.instances[obj]
  97.  
  98. class DeferredStr(str):
  99.     def __new__(cls, instance, attribute):
  100.         if not isinstance(getattr(type(instance), attribute), DeferredStrProperty):
  101.             setattr(type(instance), attribute, DeferredStrProperty(attribute))
  102.         DeferredStrProperty.instances[instance] = s = super().__new__(cls, 'x')
  103.         return s
  104.  
  105. class Test:
  106.     value: Optional[str] = None
  107.  
  108. instance = Test()
  109. instance2 = Test()
  110. deferred_str = DeferredStr(instance, "value")
  111. print("2" + deferred_str)
  112. print("".join((deferred_str,)))
  113. print(instance.value)
  114. print('some time later...')
  115. instance2.value = '3'
  116. instance.value = '1'
  117. print(instance2.value)
  118. print(deferred_str)
  119. print(deferred_str + "2")
  120. print("".join(deferred_str))
  121. print("2" + deferred_str)
  122. print("".join((deferred_str,)))
  123.  
Success #stdin #stdout 0.04s 10856KB
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Standard input is empty
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2x
x
x
some time later...
3
1
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https://ideone.com/S1en5h
language:
Python 3 (python  3.12)
created:
1 year ago
visibility:
secret

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