Learn Python the Hard Way: A Very Simple Introduction to the Terrifyingly Beautiful World of Computers and Code (Zed Shaw's Hard Way Series) by Zed A. Shaw

Author:Zed A. Shaw [Shaw, Zed A.]
Language: eng
Format: azw3
Publisher: Pearson Education
Published: 2013-09-27T00:00:00+00:00

How This Looks in Code

This is a weird concept, but to be very honest, you only have to worry about it when you make new classes and when you use a class. I will show you two tricks to help you figure out whether something is a class or object.

First, you need to learn two catch phrases: “is-a” and “has-a.” You use the phrase is-a when you talk about objects and classes being related to each other by a class relationship. You use has-a when you talk about objects and classes that are related only because they reference each other.

Now, go through this piece of code and replace each ## ?? comment with a replacement comment that says whether the next line represents an is-a or a has-a relationship and what that relationship is. In the beginning of the code, I’ve laid out a few examples, so you just have to write the remaining ones.

Remember, is-a is the relationship between Fish and Salmon, while has-a is the relationship between Salmon and Gills.

Click here to view code image

ex42.py

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