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from collections import UserDict, UserList
__all__ = ["LazyDict", "LazyList"]
class LazyDict(UserDict):
def __init__(self, data):
super().__init__()
self.data = data
def __getitem__(self, k):
v = self.data[k]
if callable(v):
v = v(k)
self.data[k] = v
return v
class LazyList(UserList):
def __getitem__(self, k):
if isinstance(k, slice):
indices = range(*k.indices(len(self)))
return [self[i] for i in indices]
v = self.data[k]
if callable(v):
v = v(k)
self.data[k] = v
return v
def __add__(self, other):
if isinstance(other, LazyList):
other = list(other)
elif isinstance(other, list):
pass
else:
return NotImplemented
return list(self) + other
def __radd__(self, other):
if not isinstance(other, list):
return NotImplemented
return other + list(self)
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