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various minor errors in iterators chapter [thanks G.P.]
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Mark Pilgrim
+12
-12
@@ -101,7 +101,7 @@ class Fib:
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<ol>
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<li>You are creating an instance of the <code>Fib</code> class (defined in the <code>fibonacci2</code> module) and assigning the newly created instance to the variable <var>fib</var>. You are passing one parameter, <code>100</code>, which will end up as the <var>max</var> argument in <code>Fib</code>’s <code>__init__()</code> method.
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<li><var>fib</var> is now an instance of the <code>Fib</code> class.
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<li>Every class instance has a built-in attribute, <code>__class__</code>, which is the object’s class. Java programmers may be familiar with the <code>Class</code> class, which contains methods like <code>getName</code> and <code>getSuperclass</code> to get metadata information about an object. In Python, this kind of metadata is available directly on the object itself through attributes like <code>__class__</code>, <code>__name__</code>, and <code>__bases__</code>.
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<li>Every class instance has a built-in attribute, <code>__class__</code>, which is the object’s class. Java programmers may be familiar with the <code>Class</code> class, which contains methods like <code>getName()</code> and <code>getSuperclass()</code> to get metadata information about an object. In Python, this kind of metadata is available through attributes, but the idea is the same.
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<li>You can access the instance’s <code>docstring</code> just as with a function or a module. All instances of a class share the same <code>docstring</code>.
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</ol>
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@@ -235,33 +235,33 @@ rules = LazyRules()</code></pre>
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<p>Let’s take the class one bite at a time.
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<pre><code>class LazyRules:
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rules_f = 'plural6-rules.txt'
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rules_filename = 'plural6-rules.txt'
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<a> def __init__(self): <span>①</span></a>
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<a> self.pattern_file = open(self.rules_f) <span>③</span></a>
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<a> self.cache = [] <span>②</span></a></code></pre>
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<a> def __init__(self): <span>①</span></a>
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<a> self.pattern_file = open(self.rules_filename) <span>③</span></a>
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<a> self.cache = [] <span>②</span></a></code></pre>
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<ol>
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<li>The <code>__init__()</code> method is only going to be called once, when you instantiate the class and assign it to <var>rules</var>.
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<li>Since this is only going to get called once, it’s the perfect place to open the pattern file. You’ll read it later; no point doing more than you absolutely have to until absolutely necessary!
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<li>Also, this is a good place to initialize the cache, which you’ll use later as you read the patterns from the pattern file.
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</ol>
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<p>Before we continue, let’s take a closer look at <var>rules_f</var>. It’s not defined within the <code>__init__()</code> method. In fact, it’s not defined within <em>any</em> method. It’s defined at the class level. It’s a <i>class variable</i>, and although you can access it just like an instance variable (<var>self.rules_f</var>), it is shared across all instances of the <code>LazyRules</code> class.
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<p>Before we continue, let’s take a closer look at <var>rules_filename</var>. It’s not defined within the <code>__init__()</code> method. In fact, it’s not defined within <em>any</em> method. It’s defined at the class level. It’s a <i>class variable</i>, and although you can access it just like an instance variable (<var>self.rules_filename</var>), it is shared across all instances of the <code>LazyRules</code> class.
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<pre class=screen>
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<samp class=p>>>> </samp><kbd>import plural6</kbd>
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<samp class=p>>>> </samp><kbd>r1 = plural6.LazyRules()</kbd>
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<samp class=p>>>> </samp><kbd>r2 = plural6.LazyRules()</kbd>
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<samp class=p>>>> </samp><kbd>r1.rules_f</kbd> <span>①</span>
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<samp class=p>>>> </samp><kbd>r1.rules_filename</kbd> <span>①</span>
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<samp>'plural6-rules.txt'</samp>
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<samp class=p>>>> </samp><kbd>r2.rules_f</kbd>
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<samp class=p>>>> </samp><kbd>r2.rules_filename</kbd>
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<samp>'plural6-rules.txt'</samp>
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<samp class=p>>>> </samp><kbd>r1.__class__.rules_f</kbd> <span>②</span>
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<samp class=p>>>> </samp><kbd>r1.__class__.rules_filename</kbd> <span>②</span>
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<samp>'plural6-rules.txt'</samp>
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<samp class=p>>>> </samp><kbd>r1.__class__.rules_f = 'papayawhip.txt'</kbd> <span>③</span>
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<samp class=p>>>> </samp><kbd>r1.rules_f</kbd>
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<samp class=p>>>> </samp><kbd>r1.__class__.rules_filename = 'papayawhip.txt'</kbd> <span>③</span>
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<samp class=p>>>> </samp><kbd>r1.rules_filename</kbd>
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<samp>'papayawhip.txt'</samp>
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<samp class=p>>>> </samp><kbd>r2.rules_f</kbd> <span>④</span>
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<samp class=p>>>> </samp><kbd>r2.rules_filename</kbd> <span>④</span>
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<samp>'papayawhip.txt'</samp></pre>
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<ol>
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<li>FIXME
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