blocks|key|353456|text|使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|353457|import+color

class+Color(color.Color):
++++...|code-block|syntax|javascript|353458|如果这是Python2.x，您还需要从object派生color.Color，使其成为new-style+class|offset|length|style|CODE|353459|class+Color(object):
++++...|353460|这在Python+3.x中不是必需的。|353461|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/54867/old-style-and-new-style-classes-in-python^0|0|0|J|6|R|B|17|F|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@$I|11|J|12|K|L]|$I|13|J|14|K|L]]|9|@$I|15|J|16|1|17]]|A|$]]|$1|M|3|N|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|19|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1A|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

Use:

<pre><code>import color

class Color(color.Color):
 ...
</code></pre>

If this were Python 2.x, you would also want to derive <code>color.Color</code> from <code>object</code>, to make it a <a href="https://stackoverflow.com/questions/54867/old-style-and-new-style-classes-in-python">new-style class</a>:

<pre><code>class Color(object):
 ...
</code></pre>

This is not necessary in Python 3.x.

blocks|key|135692|text|扩展(特别是添加新方法，而不是更改现有方法)类的另一种方法是使用预处理器，该预处理器添加了在Python本身的作用域之外/之上进行扩展的能力，在Python真正看到它之前将扩展转换为标准的Python语法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|135693|例如，我这样做是为了扩展Python2的str()类。str()是一个特别有趣的目标，因为它隐式地链接到引用的数据，比如'this'和'that'。|offset|length|style|CODE|135694|下面是一些扩展代码，其中唯一添加的非Python语法是extend:testDottedQuad位：|135695|extend:testDottedQuad
def+testDottedQuad(strObject):
++++if+not+isinstance(strObject,+basestring):+return+False
++++listStrings+=+strObject.split('.')
++++if+len(listStrings)+!=+4:+return+False
++++for+strNum+in+listStrings:
++++++++try:++++val+=+int(strNum)
++++++++except:+return+False
++++++++if+val+<+0:+return+False
++++++++if+val+>+255:+return+False
++++return+True|code-block|syntax|javascript|135696|然后我可以将代码输入到预处理器中：|135697|if+'192.168.1.100'.testDottedQuad():
++++doSomething()

dq+=+'216.126.621.5'
if+not+dq.testDottedQuad():
++++throwWarning();

dqt+=+''.join(['127','.','0','.','0','.','1']).testDottedQuad()
if+dqt:
++++print+'well,+that+was+fun'|135698|预处理器吃掉它，在没有monkeypatching的情况下输出普通的Python，Python做我想要做的事情。|135699|正如c预处理器向c添加功能一样，Python预处理器也可以向Python添加功能。|135700|我的预处理器实现对于堆栈溢出答案来说太大了，但是对于那些可能感兴趣的人来说，它是GitHub上的here。|135701|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/fyngyrz/pyex^0|0|K|5|R|5|1O|6|1V|6|0|R|L|0|0|0|0|0|0|1C|4|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@$D|18|E|19|F|G]|$D|1A|E|1B|F|G]|$D|1C|E|1D|F|G]|$D|1E|E|1F|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1G|8|@$D|1H|E|1I|F|G]]|9|@]|A|$]]|$1|J|3|K|5|L|7|1J|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|1K|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|1L|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|1M|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1N|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1O|8|@]|9|@$D|1P|E|1Q|1|1R]]|A|$]]|$1|Y|3|-4|5|6|7|1S|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

Another way to extend (specifically meaning, add new methods, not change existing ones) classes, even built-in ones, is to use a preprocessor that adds the ability to extend out of/above the scope of Python itself, converting the extension to normal Python syntax before Python actually gets to see it.

I've done this to extend Python 2's <code>str()</code> class, for instance. <code>str()</code> is a particularly interesting target because of the implicit linkage to quoted data such as <code>'this'</code> and <code>'that'</code>.

Here's some extending code, where the only added non-Python syntax is the <code>extend:testDottedQuad</code> bit:

<pre><code>extend:testDottedQuad
def testDottedQuad(strObject):
 if not isinstance(strObject, basestring): return False
 listStrings = strObject.split('.')
 if len(listStrings) != 4: return False
 for strNum in listStrings:
 try: val = int(strNum)
 except: return False
 if val &lt; 0: return False
 if val &gt; 255: return False
 return True
</code></pre>

After which I can write in the code fed to the preprocessor:

<pre><code>if '192.168.1.100'.testDottedQuad():
 doSomething()

dq = '216.126.621.5'
if not dq.testDottedQuad():
 throwWarning();

dqt = ''.join(['127','.','0','.','0','.','1']).testDottedQuad()
if dqt:
 print 'well, that was fun'
</code></pre>

The preprocessor eats that, spits out normal Python without monkeypatching, and Python does what I intended it to do.

Just as a c preprocessor adds functionality to c, so too can a Python preprocessor add functionality to Python.

My preprocessor implementation is too large for a stack overflow answer, but for those who might be interested, it is <a href="https://github.com/fyngyrz/pyex" rel="nofollow noreferrer">here</a> on GitHub.

blocks|key|135736|text|class+MyParent:

++++def+sayHi():
++++++++print('Mamma+says+hi')|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|135737|from+path.to.MyParent+import+MyParent

class+ChildClass(MyParent):
++++pass|135738|然后，ChildClass的一个实例将继承sayHi()方法。|unstyled|offset|length|style|CODE|135739|entityMap^0|0|0|3|A|L|7|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|6|7|P|8|@]|9|@]|A|$B|C]]|$1|F|3|G|5|H|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|H|7|V|8|@]|9|@]|A|$]]]|N|$]]

<pre><code>class MyParent:

 def sayHi():
 print('Mamma says hi')
</code></pre>
<pre><code>from path.to.MyParent import MyParent

class ChildClass(MyParent):
 pass
</code></pre>
An instance of <code>ChildClass</code> will then inherit the <code>sayHi()</code> method.

blocks|key|135784|text|我是这样使用它的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|135785|class+menssagem:
++propriedade1+=+"Certo!"
++propriedade2+=+"Erro!"

def+metodo1(self)
++print(self.propriedade1)|code-block|syntax|javascript|135786|来延伸。|135787|import+menssagem
class+menssagem2(menssagem):

++menssagem1+=+None+#não+nescessario+not+necessary

++def+__init__(self,menssagem):
++++self.menssagem1+=+menssagem

++#call+first+class+method
++#usando+o+metodo+da+menssagem+1

++def+Menssagem(self):
++++self.menssagem1.metodo1()|135788|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I use it like this.
<pre><code>class menssagem:
 propriedade1 = &quot;Certo!&quot;
 propriedade2 = &quot;Erro!&quot;

def metodo1(self)
 print(self.propriedade1)
</code></pre>
to extend.
<pre><code>import menssagem
class menssagem2(menssagem):

 menssagem1 = None #não nescessario not necessary

 def __init__(self,menssagem):
 self.menssagem1 = menssagem

 #call first class method
 #usando o metodo da menssagem 1

 def Menssagem(self):
 self.menssagem1.metodo1()
</code></pre>

In python how can you extend a class? For example if I have

color.py

<pre><code>class Color:
 def __init__(self, color):
 self.color = color
 def getcolor(self):
 return self.color
</code></pre>

color_extended.py

<pre><code>import Color

class Color:
 def getcolor(self):
 return self.color + " extended!"
</code></pre>

But this doesn't work...
I expect that if I work in <code>color_extended.py</code>, then when I make a color object and use the <code>getcolor</code> function then it will return the object with the string " extended!" in the end. Also it should have gotton the init from the import.

Assume python 3.1

Thanks

How to extend a class in python?

在python中，如何扩展类？例如，如果我有color.pyclass Color:    def __init__(self, color):        self.color = color    def getcolor(self):        return self.colorcolor_extended...

问如何在python中扩展类？
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