Python Objects - or what's with the periods everywhere?

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Most things in Python are objects. But what is an object?

Every constant, variable, or function in Python is actually a object with a

type and associated attributes and methods. An *attribute* a property of

the object that you get or set by giving the <object_name> + dot +

<attribute_name>, for example ``img.shape``. A *method* is a function

that the object provides, for example ``img.argmax(axis=0)`` or ``img.min()``.

Use tab completion in IPython to inspect objects and start to understand

attributes and methods. To start off create a list of 4 numbers::

a = [3, 1, 2, 1]

a.<TAB>

This will show the available attributes and methods for the Python list

``a``. **Using <TAB>-completion and help is a very efficient way to learn and later

remember object methods!**

::

In [17]: a.<TAB>

a.append a.extend a.insert a.remove a.sort

a.count a.index a.pop a.reverse

Here you see useful looking functions like ``append`` or ``sort`` which

you can get help for and use::

a.sort

a.sort?

a.sort()

a

You can tell the difference between an attribute and a callable method with

the callable function::

callable(a.sort)

[x for x in dir(a) if callable(getattr(a, x)) and not x.startswith('__')]

*Mention classes and objects as class instances?*