我已经了解到，可以在Python中向现有对象（即，不在类定义中）添加方法。
我明白这样做并不总是好的。但你怎么能做到这一点呢？
当前回答
整合Jason Pratt和社区wiki的答案，看看不同绑定方法的结果：
特别注意将绑定函数添加为类方法是如何工作的，但引用范围不正确。
#!/usr/bin/python -u
import types
import inspect
## dynamically adding methods to a unique instance of a class
# get a list of a class's method type attributes
def listattr(c):
for m in [(n, v) for n, v in inspect.getmembers(c, inspect.ismethod) if isinstance(v,types.MethodType)]:
print m[0], m[1]
# externally bind a function as a method of an instance of a class
def ADDMETHOD(c, method, name):
c.__dict__[name] = types.MethodType(method, c)
class C():
r = 10 # class attribute variable to test bound scope
def __init__(self):
pass
#internally bind a function as a method of self's class -- note that this one has issues!
def addmethod(self, method, name):
self.__dict__[name] = types.MethodType( method, self.__class__ )
# predfined function to compare with
def f0(self, x):
print 'f0\tx = %d\tr = %d' % ( x, self.r)
a = C() # created before modified instnace
b = C() # modified instnace
def f1(self, x): # bind internally
print 'f1\tx = %d\tr = %d' % ( x, self.r )
def f2( self, x): # add to class instance's .__dict__ as method type
print 'f2\tx = %d\tr = %d' % ( x, self.r )
def f3( self, x): # assign to class as method type
print 'f3\tx = %d\tr = %d' % ( x, self.r )
def f4( self, x): # add to class instance's .__dict__ using a general function
print 'f4\tx = %d\tr = %d' % ( x, self.r )
b.addmethod(f1, 'f1')
b.__dict__['f2'] = types.MethodType( f2, b)
b.f3 = types.MethodType( f3, b)
ADDMETHOD(b, f4, 'f4')
b.f0(0) # OUT: f0 x = 0 r = 10
b.f1(1) # OUT: f1 x = 1 r = 10
b.f2(2) # OUT: f2 x = 2 r = 10
b.f3(3) # OUT: f3 x = 3 r = 10
b.f4(4) # OUT: f4 x = 4 r = 10
k = 2
print 'changing b.r from {0} to {1}'.format(b.r, k)
b.r = k
print 'new b.r = {0}'.format(b.r)
b.f0(0) # OUT: f0 x = 0 r = 2
b.f1(1) # OUT: f1 x = 1 r = 10 !!!!!!!!!
b.f2(2) # OUT: f2 x = 2 r = 2
b.f3(3) # OUT: f3 x = 3 r = 2
b.f4(4) # OUT: f4 x = 4 r = 2
c = C() # created after modifying instance
# let's have a look at each instance's method type attributes
print '\nattributes of a:'
listattr(a)
# OUT:
# attributes of a:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x000000000230FD88>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x000000000230FD88>>
# f0 <bound method C.f0 of <__main__.C instance at 0x000000000230FD88>>
print '\nattributes of b:'
listattr(b)
# OUT:
# attributes of b:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x000000000230FE08>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x000000000230FE08>>
# f0 <bound method C.f0 of <__main__.C instance at 0x000000000230FE08>>
# f1 <bound method ?.f1 of <class __main__.C at 0x000000000237AB28>>
# f2 <bound method ?.f2 of <__main__.C instance at 0x000000000230FE08>>
# f3 <bound method ?.f3 of <__main__.C instance at 0x000000000230FE08>>
# f4 <bound method ?.f4 of <__main__.C instance at 0x000000000230FE08>>
print '\nattributes of c:'
listattr(c)
# OUT:
# attributes of c:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x0000000002313108>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x0000000002313108>>
# f0 <bound method C.f0 of <__main__.C instance at 0x0000000002313108>>
就我个人而言，我更喜欢外部ADDMETHOD函数路由，因为它也允许我在迭代器中动态分配新的方法名。
def y(self, x):
pass
d = C()
for i in range(1,5):
ADDMETHOD(d, y, 'f%d' % i)
print '\nattributes of d:'
listattr(d)
# OUT:
# attributes of d:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x0000000002303508>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x0000000002303508>>
# f0 <bound method C.f0 of <__main__.C instance at 0x0000000002303508>>
# f1 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
# f2 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
# f3 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
# f4 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
其他回答
在Python中，猴痘通常通过用自己的签名覆盖类或函数的签名来工作。以下是Zope Wiki的示例：
from SomeOtherProduct.SomeModule import SomeClass
def speak(self):
return "ook ook eee eee eee!"
SomeClass.speak = speak
此代码将覆盖/创建类中名为speak的方法。在Jeff Atwood最近发表的关于猴子修补的文章中，他展示了一个C#3.0的例子，这是我当前工作中使用的语言。
整合Jason Pratt和社区wiki的答案，看看不同绑定方法的结果：
特别注意将绑定函数添加为类方法是如何工作的，但引用范围不正确。
#!/usr/bin/python -u
import types
import inspect
## dynamically adding methods to a unique instance of a class
# get a list of a class's method type attributes
def listattr(c):
for m in [(n, v) for n, v in inspect.getmembers(c, inspect.ismethod) if isinstance(v,types.MethodType)]:
print m[0], m[1]
# externally bind a function as a method of an instance of a class
def ADDMETHOD(c, method, name):
c.__dict__[name] = types.MethodType(method, c)
class C():
r = 10 # class attribute variable to test bound scope
def __init__(self):
pass
#internally bind a function as a method of self's class -- note that this one has issues!
def addmethod(self, method, name):
self.__dict__[name] = types.MethodType( method, self.__class__ )
# predfined function to compare with
def f0(self, x):
print 'f0\tx = %d\tr = %d' % ( x, self.r)
a = C() # created before modified instnace
b = C() # modified instnace
def f1(self, x): # bind internally
print 'f1\tx = %d\tr = %d' % ( x, self.r )
def f2( self, x): # add to class instance's .__dict__ as method type
print 'f2\tx = %d\tr = %d' % ( x, self.r )
def f3( self, x): # assign to class as method type
print 'f3\tx = %d\tr = %d' % ( x, self.r )
def f4( self, x): # add to class instance's .__dict__ using a general function
print 'f4\tx = %d\tr = %d' % ( x, self.r )
b.addmethod(f1, 'f1')
b.__dict__['f2'] = types.MethodType( f2, b)
b.f3 = types.MethodType( f3, b)
ADDMETHOD(b, f4, 'f4')
b.f0(0) # OUT: f0 x = 0 r = 10
b.f1(1) # OUT: f1 x = 1 r = 10
b.f2(2) # OUT: f2 x = 2 r = 10
b.f3(3) # OUT: f3 x = 3 r = 10
b.f4(4) # OUT: f4 x = 4 r = 10
k = 2
print 'changing b.r from {0} to {1}'.format(b.r, k)
b.r = k
print 'new b.r = {0}'.format(b.r)
b.f0(0) # OUT: f0 x = 0 r = 2
b.f1(1) # OUT: f1 x = 1 r = 10 !!!!!!!!!
b.f2(2) # OUT: f2 x = 2 r = 2
b.f3(3) # OUT: f3 x = 3 r = 2
b.f4(4) # OUT: f4 x = 4 r = 2
c = C() # created after modifying instance
# let's have a look at each instance's method type attributes
print '\nattributes of a:'
listattr(a)
# OUT:
# attributes of a:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x000000000230FD88>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x000000000230FD88>>
# f0 <bound method C.f0 of <__main__.C instance at 0x000000000230FD88>>
print '\nattributes of b:'
listattr(b)
# OUT:
# attributes of b:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x000000000230FE08>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x000000000230FE08>>
# f0 <bound method C.f0 of <__main__.C instance at 0x000000000230FE08>>
# f1 <bound method ?.f1 of <class __main__.C at 0x000000000237AB28>>
# f2 <bound method ?.f2 of <__main__.C instance at 0x000000000230FE08>>
# f3 <bound method ?.f3 of <__main__.C instance at 0x000000000230FE08>>
# f4 <bound method ?.f4 of <__main__.C instance at 0x000000000230FE08>>
print '\nattributes of c:'
listattr(c)
# OUT:
# attributes of c:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x0000000002313108>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x0000000002313108>>
# f0 <bound method C.f0 of <__main__.C instance at 0x0000000002313108>>
就我个人而言，我更喜欢外部ADDMETHOD函数路由，因为它也允许我在迭代器中动态分配新的方法名。
def y(self, x):
pass
d = C()
for i in range(1,5):
ADDMETHOD(d, y, 'f%d' % i)
print '\nattributes of d:'
listattr(d)
# OUT:
# attributes of d:
# __init__ <bound method C.__init__ of <__main__.C instance at 0x0000000002303508>>
# addmethod <bound method C.addmethod of <__main__.C instance at 0x0000000002303508>>
# f0 <bound method C.f0 of <__main__.C instance at 0x0000000002303508>>
# f1 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
# f2 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
# f3 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
# f4 <bound method ?.y of <__main__.C instance at 0x0000000002303508>>
至少有两种方法可以将方法附加到没有类型的实例。MethodType：
>>> class A:
... def m(self):
... print 'im m, invoked with: ', self
>>> a = A()
>>> a.m()
im m, invoked with: <__main__.A instance at 0x973ec6c>
>>> a.m
<bound method A.m of <__main__.A instance at 0x973ec6c>>
>>>
>>> def foo(firstargument):
... print 'im foo, invoked with: ', firstargument
>>> foo
<function foo at 0x978548c>
1:
>>> a.foo = foo.__get__(a, A) # or foo.__get__(a, type(a))
>>> a.foo()
im foo, invoked with: <__main__.A instance at 0x973ec6c>
>>> a.foo
<bound method A.foo of <__main__.A instance at 0x973ec6c>>
2:
>>> instancemethod = type(A.m)
>>> instancemethod
<type 'instancemethod'>
>>> a.foo2 = instancemethod(foo, a, type(a))
>>> a.foo2()
im foo, invoked with: <__main__.A instance at 0x973ec6c>
>>> a.foo2
<bound method instance.foo of <__main__.A instance at 0x973ec6c>>
有用的链接：数据模型-调用描述符描述符操作指南-调用描述符
除了其他人所说的，我发现__repr_和__str__方法不能在对象级别上进行猴痘，因为repr（）和str（）使用类方法，而不是本地绑定的对象方法：
# Instance monkeypatch
[ins] In [55]: x.__str__ = show.__get__(x)
[ins] In [56]: x
Out[56]: <__main__.X at 0x7fc207180c10>
[ins] In [57]: str(x)
Out[57]: '<__main__.X object at 0x7fc207180c10>'
[ins] In [58]: x.__str__()
Nice object!
# Class monkeypatch
[ins] In [62]: X.__str__ = lambda _: "From class"
[ins] In [63]: str(x)
Out[63]: 'From class'
我相信你要找的是setattr。使用此设置对象的属性。
>>> def printme(s): print repr(s)
>>> class A: pass
>>> setattr(A,'printme',printme)
>>> a = A()
>>> a.printme() # s becomes the implicit 'self' variable
< __ main __ . A instance at 0xABCDEFG>
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