A decorator to check a method's object attribute before executing its body.

checkdecorator.py

def check(attr):
    def _check_fn(fn):
        """Use this function as a method decorator. When decorated with this, a
        method will only execute its body when its associated object's attribute
        is defined (evaluates to True).

        """
        def meth(self, *args, **kwargs):
            if getattr(self, attr, None):
                return fn(self, *args, **kwargs)
        return meth
    return _check_fn


class Foo(object):

    def __init__(self, _foo):
        self._foo = _foo

    @check('_foo')
    def foo(self):
        """Examples:

        >>> from decometh import Foo
        >>> f = Foo('Hello')
        >>> f.foo()
        'Hello'
        >>> f = Foo(None)
        >>> f.foo()
        >>>
        """
        return self._foo