Python动态添加到函数 [英] Python add to a function dynamically

问题描述

如何在之前或之后向现有功能添加代码?

how do i add code to an existing function, either before or after?

例如，我有一堂课:

 class A(object):
     def test(self):
         print "here"

我该如何编辑带有元编程的类，这样我就可以做到

how do i edit the class wit metaprogramming so that i do this

 class A(object):
     def test(self):
         print "here"

         print "and here"

也许可以通过某种方式附加另一个功能进行测试?

maybe some way of appending another function to test?

添加另一个功能，例如

 def test2(self):
      print "and here"

并将原件更改为

 class A(object):
     def test(self):
         print "here"
         self.test2()

有没有办法做到这一点?

is there a way to do this?

推荐答案

如果需要，可以使用装饰器来修改函数.但是，由于它不是在函数初始定义时应用的修饰符，因此您将无法使用@语法糖来应用它.

You can use a decorator to modify the function if you want. However, since it's not a decorator applied at the time of the initial definition of the function, you won't be able to use the @ syntactic sugar to apply it.

>>> class A(object):
...     def test(self):
...         print "orig"
...
>>> first_a = A()
>>> first_a.test()
orig
>>> def decorated_test(fn):
...     def new_test(*args, **kwargs):
...         fn(*args, **kwargs)
...         print "new"
...     return new_test
...
>>> A.test = decorated_test(A.test)
>>> new_a = A()
>>> new_a.test()
orig
new
>>> first_a.test()
orig
new

请注意，它也会修改现有实例的方法.

Do note that it will modify the method for existing instances as well.

编辑:使用args和kwargs

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