https://github.com/szhu/cachedproperty

You Only Compute Once that's the motto
https://github.com/szhu/cachedproperty

Last synced: about 1 month ago
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You Only Compute Once that's the motto

• Host: GitHub
• URL: https://github.com/szhu/cachedproperty
• Owner: szhu
• Created: 2014-11-17T09:28:47.000Z (about 10 years ago)
• Default Branch: master
• Last Pushed: 2014-11-17T09:31:26.000Z (about 10 years ago)
• Last Synced: 2024-04-11T15:52:48.924Z (9 months ago)
• Language: Python
• Homepage:
• Size: 113 KB
• Stars: 1
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
@cachedproperty

===============

Python attributes are cached. Python property methods are lazy. Can't we have both?

`@cachedproperty` computes your attributes the first time they're accessed, because sometimes you'll never need to access them. It doubles as a dependency manager – no need to compute attributes in the correct order in `__init__`. (No circular dependencies, please!)

`@cachedproperty` is a decorator – use it just like `@property`:

```python

from cachedproperty import cachedproperty, ObjectWithCachedProperties

class NetworkUTCTime(ObjectWithCachedProperties):

    @cachedproperty

    def as_string(self):

        from urllib2 import urlopen

        print "getting time from timeapi.org"

        response = urlopen('http://www.timeapi.org/utc/now')

        return response.read()

    @cachedproperty

    def as_datetime(self):

        print "converting time from str to datetime"

        from dateutil.parser import parse

        return parse(self.as_string)

```

...except code won't run more than once!

```python

>>> t = NetworkUTCTime()

>>> t.as_datetime

converting time from str to datetime

getting time from timeapi.org

datetime.datetime(2014, 11, 17, 9, 21, 27, tzinfo=tzutc())

>>> t.as_string

'2014-11-17T09:21:27+00:00'

>>> t.as_datetime

datetime.datetime(2014, 11, 17, 9, 21, 27, tzinfo=tzutc())

```