[Tutor] What's the correct way to define/access methods of a member variable in a class pointing to an object?

[Sharad Singla]

Hi Pythonistas

What's the correct way to define/access methods of a member variable in a
class pointing to an object?

For example, I have a class Foo that has a method foo_method:

class Foo:
    def foo_method(self):
        return 'bar'

Now, in another class Bar, I'd like to store an object to this class (I do
not want Bar to inherit Foo).

What is the correct/recommended way to define class Bar?

class Bar:
    def __init__(self):
        self.foo = Foo()
# OR
class Bar:
    def __init__(self):
        self.foo = Foo()

    def bar_method(self):
        return self.foo.bar()

The former will allow me to use:

x = Bar()
x.foo.foo_method()

But, with this I'm directly accessing methods of a member variable (strong
coupling).

The benefits I see with this approach are:

   - I don't have to wrap every new method that gets added to class Foo.
   - Bar may contain more member variables pointing to other classes. Not
   wrapping them keeps Bar smaller and manageable in size.
   - The auto-completion facility from IDE (PyCharm, etc.) or IPython helps
   inspect bar like a menu (x.foo) followed by a sub-menu (
   x.foo.foo_method(), x.bar.foobar(), etc.) making it easier to develop
   code.
   - Functional programming look-n-feel (not sure if this a pro or con)

The cons are strong coupling, not encapsulating internal details of foo,
etc.

I wanted to check if this a recommended practice? And/or if there are any
guidelines related to this (kind of implementing a composite pattern)?

There may be more classes (Bat(), etc.) in future and I'd like to extend
Foo in future to store an object of these classes. Foo() is a part of a
library and my intent is to make Foo() as the entry point for the target
users (to allow them auto-completion via dotted notation) rather than
having them remember all the classes Bar(), Bat(), etc.

Any inputs/pointers will be highly appreciated!


Regards

Sharad


PS> I've posted this in SO at
http://stackoverflow.com/questions/39231932/whats-the-correct-way-to-access-methods-of-a-member-variable-in-a-class-pointin/39237874#39237874
but I'm looking for more information/ideas/thoughts/opinions on this.