A cached-property for decorating methods in classes.
Project description
A cached-property for decorating methods in classes.
- Free software: BSD license
- Documentation: http://cached-property.rtfd.org.
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
Define a class with an expensive property. Every time you stay there the price goes up by $50. I
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:
>>> m = Monopoly() >>> m.boardwalk 550 >>> m.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 @property def cached_property(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.
>>> m = Monopoly() >>> m.boardwalk 550 >>> m.boardwalk 550 >>> m.boardwalk 550
Why doesn’t the value of m.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.
History
0.1.1 (2014-05-17)
- setup.py fix. Whoops!
0.1.0 (2014-05-17)
- First release on PyPI.
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