Python Objects - Or What's With The Periods Everywhere?

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Python Objects - or what’s with the periods everywhere?¶

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?

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