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Mark Pilgrim
171 lines
6.1 KiB
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171 lines
6.1 KiB
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<title>Advanced Classes - Dive into Python 3</title>
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<p>You are here: <a href=index.html>Home</a> <span class=u>‣</span> <a href=table-of-contents.html#advanced-classes>Dive Into Python 3</a> <span class=u>‣</span>
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<p id=level>Difficulty level: <span title=advanced>♦♦♦♦♢</span>
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<h1>Advanced Classes</h1>
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<blockquote class=q>
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<p><span class=u>❝</span> FIXME <span class=u>❞</span><br>— FIXME
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</blockquote>
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<p id=toc>
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<h2 id=divingin>Diving In</h2>
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<p class=f>FIXME
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<h2 id=ordereddict>Ordered Dictionary: Not An Oxymoron</h2>
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<p>[FIXME here's why ordered dicts are useful: http://www.gossamer-threads.com/lists/python/dev/656556 ]
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<p class=d>[<a href=examples/ordereddict.py>download <code>ordereddict.py</code></a>]
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<pre><code class=pp>import collections
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import itertools
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class OrderedDict(dict, collections.MutableMapping):
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def __init__(self, *args, **kwds):
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if len(args) > 1:
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raise TypeError('expected at most 1 arguments')
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if not hasattr(self, '_keys'):
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self._keys = []
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self.update(*args, **kwds)
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def clear(self):
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del self._keys[:]
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dict.clear(self)
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def __setitem__(self, key, value):
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if key not in self:
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self._keys.append(key)
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dict.__setitem__(self, key, value)
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def __delitem__(self, key):
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dict.__delitem__(self, key)
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self._keys.remove(key)
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def __iter__(self):
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return iter(self._keys)
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def __reversed__(self):
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return reversed(self._keys)
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def popitem(self):
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if not self:
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raise KeyError('dictionary is empty')
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key = self._keys.pop()
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value = dict.pop(self, key)
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return key, value
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def __reduce__(self):
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items = [[k, self[k]] for k in self]
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inst_dict = vars(self).copy()
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inst_dict.pop('_keys', None)
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return (self.__class__, (items,), inst_dict)
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setdefault = MutableMapping.setdefault
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update = MutableMapping.update
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pop = MutableMapping.pop
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keys = MutableMapping.keys
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values = MutableMapping.values
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items = MutableMapping.items
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def __repr__(self):
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if not self:
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return '{0}()'.format(self.__class__.__name__,)
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return '{0}({1})'.format(self.__class__.__name__, repr(list(self.items())))
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def copy(self):
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return self.__class__(self)
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@classmethod
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def fromkeys(cls, iterable, value=None):
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d = cls()
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for key in iterable:
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d[key] = value
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return d
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def __eq__(self, other):
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if isinstance(other, OrderedDict):
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return all(p==q for p, q in itertools.zip_longest(self.items(), other.items()))
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return dict.__eq__(self, other)</code></pre>
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<p class=a>⁂
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<h2 id=class-attributes>Attributes of a Class Object</h2>
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<p>FIXME
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<pre class=screen>
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<samp class=p>>>> </samp><kbd>import ordereddict</kbd>
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<samp class=p>>>> </samp><kbd>od = ordereddict.OrderedDict()</kbd>
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<a><samp class=p>>>> </samp><kbd>klass = od.__class__</kbd> <span class=u>①</span></a>
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<samp class=p>>>> </samp><kbd>type(klass)</kbd>
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<samp><class 'abc.ABCMeta'></samp>
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<samp class=p>>>> </samp><kbd>klass.__name__</kbd>
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<samp>'OrderedDict'</samp>
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<!--
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<samp class=p>>>> </samp><kbd>klass.__doc__</kbd>
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<samp>FIXME</samp>
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-->
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<samp class=p>>>> </samp><kbd>klass.__module__</kbd>
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<samp>'ordereddict'</samp>
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<samp class=p>>>> </samp><kbd>klass.__bases__</kbd>
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<samp>(<class 'dict'>, <class '_abcoll.MutableMapping'>)</samp></pre>
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<ol>
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<li>FIXME
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</ol>
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<pre class=screen>
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# continued from previous example
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<samp class=p>>>> </samp><kbd>klass.__dict__</kbd>
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<samp>{'__abstractmethods__': frozenset(),
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'__delitem__': <function __delitem__ at 0x00DCB6A8>,
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'__dict__': <attribute '__dict__' of 'OrderedDict' objects>,
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'__doc__': None,
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'__eq__': <function __eq__ at 0x00DD2930>,
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'__hash__': None,
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'__init__': <function __init__ at 0x00DC41E0>,
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'__iter__': <function __iter__ at 0x00DCB618>,
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'__module__': 'ordereddict',
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'__reduce__': <function __reduce__ at 0x00DCB6F0>,
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'__repr__': <function __repr__ at 0x00DCB8E8>,
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'__reversed__': <function __reversed__ at 0x00DCB660>,
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'__setitem__': <function __setitem__ at 0x00DCB5D0>,
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'__weakref__': <attribute '__weakref__' of 'OrderedDict' objects>,
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'_abc_cache': <_weakrefset.WeakSet object at 0x00DCF950>,
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'_abc_negative_cache': <_weakrefset.WeakSet object at 0x00DCF990>,
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'_abc_negative_cache_version': 12,
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'_abc_registry': <_weakrefset.WeakSet object at 0x00DCF910>,
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'clear': <function clear at 0x00DCB7C8>,
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'copy': <function copy at 0x00DD28A0>,
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'fromkeys': <classmethod object at 0x00DCF8F0>,
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'items': <function items at 0x00D60150>,
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'keys': <function keys at 0x00D60108>,
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'pop': <function pop at 0x00D60978>,
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'popitem': <function popitem at 0x00DCB780>,
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'setdefault': <function setdefault at 0x00D60A98>,
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'update': <function update at 0x00D60A50>,
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'values': <function values at 0x00D60198>}</samp></pre>
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<ol>
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<li>FIXME
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</ol>
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<p class=a>⁂
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<h2 id=implementing-fractions>Implementing Fractions</h2>
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<p class=v><a rel=prev class=todo><span class=u>☜</span></a> <a rel=next class=todo><span class=u>☞</span></a>
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<p class=c>© 2001–9 <a href=about.html>Mark Pilgrim</a>
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