Python Lesson 05 - Dictionaries, Multi-Dimensional Lists, and Mutability

In this Python lesson, we look at the very useful dictionary data type, as well as how to deal with lists that have multiple dimensions and a problem to avoid with lists.
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Plug into BitMerge

[anthonyflury]

quick correction - although maybe a bit too deep for a beginner : You can't use any data type as a key into a dictionary - it has to be a hashable data type. In general most basic types are hashables, but for instance lists are not hashable, and custom objects aren't hashable by default.

[anthonyflury]

You got it wrong when you said that when you do x = y = 10, that x & y get 'copies' - they don't - they both refer to the same '10' integer object, the same as later x & y end up referring to the same list. The difference between the two examples is that because the '10' integer is immutable, that when you do x=55 - you are end up rebinding x to a new object - becuase it's original object cannot be changed. In Python everything name is a reference to an object - nothing more and nothing less.. I cover this and other stuff in my blog post :

You might not want to get deep into the detail with beginners - but you should make sure you are correct with the info that you do give them.