A cached-property for decorating methods in classes.
Project description
A cached-property for decorating methods in classes.
Why?
Makes caching of time or computational expensive properties quick and easy.
Because I got tired of copy/pasting this code from non-web project to non-web project.
I needed something really simple that worked in Python 2 and 3.
How to use it
Let’s define a class with an expensive property. Every time you stay there the price goes up by $50!
class Monopoly(object):
def __init__(self):
self.boardwalk_price = 500
@property
def boardwalk(self):
# In reality, this might represent a database call or time
# intensive task like calling a third-party API.
self.boardwalk_price += 50
return self.boardwalk_price
Now run it:
>>> monopoly = Monopoly()
>>> monopoly.boardwalk
550
>>> monopoly.boardwalk
600
Let’s convert the boardwalk property into a cached_property.
from cached_property import cached_property
class Monopoly(object):
def __init__(self):
self.boardwalk_price = 500
@cached_property
def boardwalk(self):
# Again, this is a silly example. Don't worry about it, this is
# just an example for clarity.
self.boardwalk_price += 50
return self.boardwalk_price
Now when we run it the price stays at $550.
>>> monopoly = Monopoly()
>>> monopoly.boardwalk
550
>>> monopoly.boardwalk
550
>>> monopoly.boardwalk
550
Why doesn’t the value of monopoly.boardwalk change? Because it’s a cached property!
Credits
Django, Werkzueg, Bottle, and Zope for having their own implementations. This package uses the Django version.
Reinout Van Rees for pointing out the cached_property decorator to me.
My awesome wife Audrey who created cookiecutter, which meant rolling this out took me just 15 minutes.
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