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descriptors.py
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descriptors.py
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class lazyattr:
"""Non-data descriptor which replaces itself with an instance attribute.
>>> class LazyBoy:
... @lazyattr
... def ayy(self):
... print('ayy')
... return 'lmao'
>>> LazyBoy.ayy # doctest: +ELLIPSIS
<descriptors.lazyattr object at ...>
>>> boy = LazyBoy()
>>> vars(boy)
{}
>>> boy.ayy
ayy
'lmao'
>>> vars(boy)
{'ayy': 'lmao'}
>>> boy.ayy
'lmao'
>>> del boy.ayy
>>> boy.ayy
ayy
'lmao'
"""
def __init__(self, method):
self.method = method
def __set_name__(self, owner, name):
# Called when `self` is set on `owner`.
self.name = name
def __get__(self, instance, owner):
if instance is None:
# Accessed via the class (`owner`), not an instance.
return self
result = self.method(instance)
setattr(instance, self.name, result)
return result