Python getattribute and wrapper of method

Question

I want to call a wrapper method of function with argument just before I call specific method. So I guess I have to ovewrite __getattribute__ method.

Here is an example of code:

def wrapper(func):
    return func * 2

class A(object):
    def test(self, arg):
        return arg + 1

    def __getattribute__(self, name):
        if name in ['test']:
            return wrapper(super(A, self).__getattribute__(name))
        return super(A, self).__getattribute__(name)

The matter is that getattribute is called when test return the value. What I want is to be able to catch test with the arguments and define the wrapper method like this:

def wrapper(func, *args, **kwargs):
    print "do some stuff"
    return func(*args, **kwargs)

Did you mean to place your parentheses as follows return wrapper(super(A, self).__getattribute__)(name)? — David Robinson
– David Robinson, Commented Sep 1, 2014 at 14:16
@DavidRobinson: no, that'd not actually retrieve the method object. Take a look at my answer, where I separate out the super() call and the wrapping. — Martijn Pieters
– Martijn Pieters, Commented Sep 1, 2014 at 14:17

Martijn Pieters · Accepted Answer · 2014-09-01 14:21:53Z

4

Use a factory function to return your wrapper:

def decorate(f):
    def wrapper(*args, **kw):
        return f(*args, **kw) * 2
    return wrapper

Here f is closed over by wrapper(), so it can access the name when called.

Then return this in the __getattribute__ hook:

def __getattribute__(self, name):
    result = super(A, self).__getattribute__(name)
    if name in ('test',):
        return decorate(result)
    return result

Of course, you could also just apply decorate as a decorator on test then:

class A(object):
    @decorate
    def test(self, arg):
        return arg + 1

edited Sep 1, 2014 at 14:21

answered Sep 1, 2014 at 14:15

Martijn Pieters

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2 Comments

Katsu Over a year ago

Ty for help. I can not change or affect wrapper (from another class). But I guess my only choice is to make a decorator on test method and I don't need to use __getattribute__.

Martijn Pieters Over a year ago

@Katsu: yes, that'd be the better option. I assumed that wasn't an option for you.

semptic · Accepted Answer · 2014-09-01 14:20:56Z

1

If I understand you correctly, you can use a decorator.

def wrapper(func):
    def _wrapper(*args, **kwargs):
        return func(*args, **kwargs) * 2

    return _wrapper

class A(object):
    @wrapper
    def test(self, arg):
        return arg + 1

answered Sep 1, 2014 at 14:20

semptic

6644 silver badges16 bronze badges

1 Comment

Katsu Over a year ago

+1: Yes it was I suggested previous comment Thank you

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