python 在python中扩展内置类
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Extending builtin classes in python
提问by UnkwnTech
How can I extend a builtin class in python?
I would like to add a method to the str class.
I've done some searching but all I'm finding is older posts, I'm hoping someone knows of something newer.
如何在 python 中扩展内置类？我想向 str 类添加一个方法。
我已经做了一些搜索，但我发现的只是较旧的帖子，我希望有人知道更新的内容。
采纳答案by S.Lott
Just subclass the type
只是将类型子类化
>>> class X(str):
... def my_method(self):
... return int(self)
...
>>> s = X("Hi Mom")
>>> s.lower()
'hi mom'
>>> s.my_method()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 3, in my_method
ValueError: invalid literal for int() with base 10: 'Hi Mom'
>>> z = X("271828")
>>> z.lower()
'271828'
>>> z.my_method()
271828
回答by lll
One way could be to use the "class reopening" concept (natively existing in Ruby) that can be implemented in Python using a class decorator. An exemple is given in this page: http://www.ianbicking.org/blog/2007/08/opening-python-classes.html
一种方法是使用“类重新打开”概念（在 Ruby 中原生存在），该概念可以使用类装饰器在 Python 中实现。本页给出了一个例子：http: //www.ianbicking.org/blog/2007/08/opening-python-classes.html
I quote:
我引用：
I think with class decorators you could do this:
我认为使用类装饰器你可以这样做：
@extend(SomeClassThatAlreadyExists)
class SomeClassThatAlreadyExists:
def some_method(self, blahblahblah):
stuff
Implemented like this:
像这样实现：
def extend(class_to_extend):
def decorator(extending_class):
class_to_extend.__dict__.update(extending_class.__dict__)
return class_to_extend
return decorator
回答by MVP
Assuming that you can not change builtin classes.
To simulate a "class reopening" like Ruby in Python3 where __dict__is an mappingproxy object and not dict object :
假设您不能更改内置类。要在 Python3 中模拟像 Ruby 这样的“类重新打开”，其中__dict__是一个 mappingproxy 对象而不是 dict 对象：
def open(cls):
def update(extension):
for k,v in extension.__dict__.items():
if k != '__dict__':
setattr(cls,k,v)
return cls
return update
class A(object):
def hello(self):
print('Hello!')
A().hello() #=> Hello!
#reopen class A
@open(A)
class A(object):
def hello(self):
print('New hello!')
def bye(self):
print('Bye bye')
A().hello() #=> New hello!
A().bye() #=> Bye bye
I could also write a decorator function 'open' as well:
我也可以编写一个装饰器函数“open”：
def open(cls):
def update(extension):
namespace = dict(cls.__dict__)
namespace.update(dict(extension.__dict__))
return type(cls.__name__,cls.__bases__,namespace)
return update
