Question

Just like the title said.
For example:
I have a class like this:

class NewClass():
    def func1():
        .....

then I want to add a new function into this class when program file running.
just like reassign a new value to the attribute of the class.
e.g.

NewClass.a = 3

Answer 1

If you want to add a function to the class type itself, you can just assign it, making sure to include the argument for the self-reference passed:

>>> class Quz(object):
...     def __init__(self):
...         self.a = "A"
...
>>> def qux(self):
...     print self.a
...
>>> Quz.qux = qux
>>> q = Quz()
>>> q.qux()
A

---

You can use types.MethodType() to create a bound instance method if you only want to add the function to a single instance of the class:

>>> import types
>>> class Foo(object):
...     def __init__(self):
...         self.a = "A"
...
>>> def bar(self):
...     print self.a
...
>>> f = Foo()
>>> f.bar = types.MethodType(bar, f, Foo)
>>> f.bar()
A