自python 2.6以来，模块new已弃用，并在3.0中删除，请使用类型

看见http://docs.python.org/library/new.html

在下面的示例中，我故意从patch_me（）函数中删除了返回值。我认为，给出返回值可能会让人相信补丁会返回一个新对象，这是不正确的——它会修改传入的对象。这可能有助于更严格地使用猴痘。

import types

class A(object):#but seems to work for old style objects too
    pass

def patch_me(target):
    def method(target,x):
        print "x=",x
        print "called from", target
    target.method = types.MethodType(method,target)
    #add more if needed

a = A()
print a
#out: <__main__.A object at 0x2b73ac88bfd0>  
patch_me(a)    #patch instance
a.method(5)
#out: x= 5
#out: called from <__main__.A object at 0x2b73ac88bfd0>
patch_me(A)
A.method(6)        #can patch class too
#out: x= 6
#out: called from <class '__main__.A'>

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>

由于这个问题是针对非Python版本提出的，这里是JavaScript：

a.methodname = function () { console.log("Yay, a new method!") }

可以使用lambda将方法绑定到实例：

def run(self):
    print self._instanceString

class A(object):
    def __init__(self):
        self._instanceString = "This is instance string"

a = A()
a.run = lambda: run(a)
a.run()

输出：

This is instance string

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

如何从类的实例恢复类

class UnderWater:
    def __init__(self):
        self.net = 'underwater'

marine = UnderWater() # Instantiate the class

# Recover the class from the instance and add attributes to it.
class SubMarine(marine.__class__):  
    def __init__(self):
        super().__init__()
            self.sound = 'Sonar'
    
print(SubMarine, SubMarine.__name__, SubMarine().net, SubMarine().sound)

# Output
# (__main__.SubMarine,'SubMarine', 'underwater', 'Sonar')