https://github.com/zbraniecki/python_baseclasses

Python's Base Classes
https://github.com/zbraniecki/python_baseclasses

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Python's Base Classes

• Host: GitHub
• URL: https://github.com/zbraniecki/python_baseclasses
• Owner: zbraniecki
• Created: 2010-12-28T07:26:10.000Z (about 14 years ago)
• Default Branch: master
• Last Pushed: 2010-12-28T07:56:16.000Z (about 14 years ago)
• Last Synced: 2024-11-25T09:14:47.824Z (2 months ago)
• Homepage:
• Size: 97.7 KB
• Stars: 2
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README

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README

        
LazyDict is a subclass of a dict that can additionally store

items in a form of a stub that is expanded on the first call.

Such class may be useful in all cases where dictionary items

are expensive to initialize and on average an application

is using only some of the elements of the dictionary.

Once the item is requested for the first time,

it is cached for later use.

Example:

    def resolver(self, key, *args, **kwargs):

        print("resolving")

        table = kwargs.pop('table', None)

        return QueryValue(table=table)

    d = LazyDict({'a': 1})

    d.set_stub('b', resolver, table='items')

    

    print(len(d))                    # 2

    x = d['b']                       # resolving

    x2 = d['b']                      #

    print(isinstance(x2, QueryValue) # True

Additionally, LazyDict provides a method to define a resolver that

will be used for all stubs that do not provide its own.

Example:

    def resolver(self, key, *args, **kwargs):

        print("resolving")

        table = kwargs.pop('table', None)

        return QueryValue(table=table)

    d = LazyDict({'a': 1})

    d.set_resolver(resolver)

    d.set_stub('b', None, table='items')

    d.set_stub('c', None, table='people')

    

    print(len(d))                    # 2

    x = d['b']                       # resolving

    x2 = d['b']                      #

    y = d['c']                       # resolving

    y2 = d['c']                      #

    print(isinstance(x2, QueryValue) # True

    print(isinstance(y2, QueryValue) # True

LazyDict provides exactly the same methods as dict and behaves very close to it.

The only difference is that in some cases it resolves its stubs.

In particular:

LazyDict does not resolve any stubs when using:

 * __init__

 * __len__

 * __setitem__

 * __delitem__

 * __contains__

 * __iter__

 * clear

 * copy

 * keys

 * update

 * __repr__

 * set_stub

 * set_resolver

LazyDict may resolve a single stub associated with the given key when using:

 * get

 * popitem

 * setdefault

 * pop

LazyDict may resolve all stubs when using:

 * __cmp__

 * __eq__

 * __getitem__

 * items

 * values

 * resolve

== Compatibility ==

LazyDict is compatible with Python 2.6+ and Python 3.0+. Its test suite is

compatible with Python 2.7+ and Python 3.0+.

Majority of code is based on Python's ABC, UserDict and OrderedDict classes.