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from functools import update_wrapper
class reify(object):
""" Use as a class method decorator. It operates almost exactly like the
Python ``@property`` decorator, but it puts the result of the method it
decorates into the instance dict after the first call, effectively
replacing the function it decorates with an instance variable. It is, in
Python parlance, a non-data descriptor. An example:
.. code-block:: python
class Foo(object):
@reify
def jammy(self):
print('jammy called')
return 1
And usage of Foo:
>>> f = Foo()
>>> print(f.jammy)
'jammy called'
1
>>> print(f.jammy)
1
>>> # jammy func not called the second time; it replaced itself with 1
Note: reassignment is possible
>>> f.jammy = 2
>>> f.jammy
2
"""
def __init__(self, wrapped):
self.wrapped = wrapped
update_wrapper(self, wrapped)
def __get__(self, inst, objtype=None):
if inst is None:
return self
val = self.wrapped(inst)
setattr(inst, self.wrapped.__name__, val)
return val
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