morepath/morepath/reify.py at path_tool · python3/morepath

46 lines (35 loc) · 1.13 KB

# Originally taken from pyramid.decorator

class reify(object):

"""Cache a property.

Use as a 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:

.. testcode::

from morepath import reify

class Foo(object):

@reify

def jammy(self):

print('jammy called')

return 1

And usage of Foo:

>>> f = Foo()

>>> v = f.jammy

jammy called

>>> print(v)

>>> print(f.jammy)

>>> # jammy func not called the second time; it replaced itself with 1

"""

def __init__(self, wrapped):

self.wrapped = wrapped

self.__doc__ = wrapped.__doc__

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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