如何在python中扩展一个类？
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How to extend a class in python?
提问by omega
In python how can you extend a class? For example if I have
在python中你如何扩展一个类？例如，如果我有
color.py
颜色.py
class Color:
def __init__(self, color):
self.color = color
def getcolor(self):
return self.color
color_extended.py
color_extended.py
import Color
class Color:
def getcolor(self):
return self.color + " extended!"
But this doesn't work...
I expect that if I work in color_extended.py, then when I make a color object and use the getcolorfunction then it will return the object with the string " extended!" in the end. Also it should have gotton the init from the import.
但这不起作用......我希望如果我在 中工作color_extended.py，那么当我创建一个颜色对象并使用该getcolor函数时，它将返回带有字符串“extended！”的对象。到底。它也应该从导入中获取 init。
Assume python 3.1
假设 python 3.1
Thanks
谢谢
采纳答案by NPE
Use:
用：
import color
class Color(color.Color):
...
If this were Python 2.x, you would also want to derive color.Colorfrom object, to make it a new-style class:
如果是这样的Python 2.x中，你也想得出color.Color的object，使它成为一个新式类：
class Color(object):
...
This is not necessary in Python 3.x.
这在 Python 3.x 中不是必需的。
回答by fyngyrz
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.
另一种扩展（特别是添加新方法，而不是更改现有方法）类，甚至是内置类的方法是使用预处理器，它增加了扩展到 Python 本身范围之外/之上的能力，将扩展转换为在 Python 真正看到它之前的正常 Python 语法。
I've done this to extend Python 2's str()class, for instance. str()is a particularly interesting target because of the implicit linkage to quoted data such as 'this'and 'that'.
例如，我这样做是为了扩展 Python 2 的str()类。str()是一个特别有趣的目标，因为它隐式链接到引用的数据，例如'this'和'that'。
Here's some extending code, where the only added non-Python syntax is the extend:testDottedQuadbit:
这是一些扩展代码，其中唯一添加的非 Python 语法是extend:testDottedQuad：
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
After which I can write in the code fed to the preprocessor:
之后，我可以写入提供给预处理器的代码：
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'
The preprocessor eats that, spits out normal Python without monkeypatching, and Python does what I intended it to do.
预处理器吃掉它，在没有猴子补丁的情况下吐出正常的 Python，Python 做我想要它做的事情。
Just as a c preprocessor adds functionality to c, so too can a Python preprocessor add functionality to Python.
正如 ac 预处理器为 c 添加功能一样，Python 预处理器也可以为 Python 添加功能。
My preprocessor implementation is too large for a stack overflow answer, but for those who might be interested, it is hereon GitHub.
我的预处理器的实施是一个堆栈溢出的答案太大，但对于那些谁可能会感兴趣，它是这里在GitHub上。
