Unit 3 Lab: Object-Oriented Programming

Overview

Welcome to the Unit 3 lab!

Our goal is that at the end of the Unit 5 lab, you'll have an app that prints out the Rotten Tomatoes rating for any movie a user enters. We're getting closer!

Right now, let's use object-oriented programming concepts to improve our code. Specifically, we'll be using dictionaries and classes.

Deliverables

You're going to continue building this locally from where you left off with the last lab. You'll write all of your code in the same movie_app.py file.

Run the file from the command line to check your work.

Reminder: On your laptop, you can run the file from your command line with the following:

python movie_app.py

Hint: Make sure you are printing something out with the print statement. Otherwise, you won't see any output from running your program!

Requirements:

You have a Movie class.
You have a Media class.
You have docstrings on each function.
Your main function prints:

The movie Back to the Future has a rating of 4
The movie Blade has a rating of 4
The movie Spirited Away has a rating of 4

Then:

If search_or_ratings is 1, your program prints an indented list of movies:
```
Back to the Future
Blade
Spirited Away
```
If search_or_ratings is 2, your program prints The rating for Moana is 7.

Directions

Augment the code you wrote for the Unit 2 lab.

Part 1: Docstrings

First, for each of your existing functions, add docstrings to document what each function does. (It doesn't hurt to add them to all functions, including main()!).
1. Remember that a docstring is made with """. For example, your main() could look like this:
```
 def main():
 """
 Main is the entry point into the program, and it calls into the search or
 ratings functions depending on what the user decides to do.
 """
```
1. As you go through this lab, update your docstrings and create new ones for new functions. It will help you, and others in the future, keep track of what each function does.

Part 2: Adding a Class

Part 2a: The Classes

First, create a Media class. This will be the parent class of Movie, and it itself will inherit from the object base python class.
The Media class will take two arguments, publisher and market, which are both strings. These strings will set class instance variables, self.publisher and self.market. Whenever this class is instantiated or called, assume values of Universal Studios for publisher and USA for market.
The Media class will have one class method, .get_media_info(). This method will print the self.publisher and self.market class instance variables to stdout and return None.
Next, create a Movie class. This class will inherit from the base Media class. We're going to have several movies, each of which will have a title and a rating. We can use a Movie class as a scaffold to create many movie objects. Near the top of your file, create a class, Movie, that takes an argument of object. Your Movie class should have three functions:
1. __init__, which will take in self, movie_data (this will be a dictionary containing the title and rating of each movie), publisher and market. __init__ will set a member variable, movie_data, to equal the movie_data dictionary passed in. publisher and market variables will be passed to the Media object, which must also have its __init__() method called using the super() builtin function.
2. get_movie_title(), a getter function that returns the value of the title key in the movie_data dictionary.
3. get_movie_rating(), a getter function that returns the value of the rating key in the movie_data dictionary.
Now that we have a Movie class with getter functions, we won't need print_movie_rating() or print_movie_title(), so delete them.
1. Then, in your main() function, set the existing elif search_or_ratings == 2: to print_single_movie_rating, and set else to print "Error: Your input must be 1 or 2!".
Now that we have a class, let's make a function that creates Movie objects.
1. Create a function called return_single_movie_object() that takes two arguments, movie_title and movie_rating.
2. Have it create and return a Movie object with those values.

Part 2b: The Class Objects

Now we can make Movie objects. Let's look at all the places we're currently using regular movie titles. Can we replace some of them with Movie objects?

First, let's look at print_all_ratings. Right now, it loops through a list of movie titles and prints out each one. We want it to make Movie objects instead, but we don't have ratings. Let's use placeholders and set each rating to 4.
1. Change print_all_ratings to loop through the movie title list and call return_single_movie_object on each title, passing in the title and 4 in the list for parameters. Then, print out "The movie", title, "has a rating of", rating). Use the object's getter functions for the title and rating.
Next, let's look at print_single_movie_rating. Right now, it prints out the variables for movie_title and movie_rating that we have declared at the top of the file. However, we're going to want it to print out the rating and title of any Movie object so that it's useful to the user when they look for a movie.
1. Change print_single_movie_rating to take in a movie title, movie_query.
2. Then, create a Movie object from the title that's passed in. In print_single_movie_rating, call return_single_movie_object on that title, with a rating of 7 (later, the rating will be accurate; for now, let's hard-code it.)
3. Now, change the print statement to use the getter functions on the new Movie object.
4. We're calling print_single_movie_rating in main(), so we'll need to change that to provide an argument. Pass it a title of a movie you like, such as "Moana".
Now that we aren't using movie_title and movie_rating at the top of the file, you can delete them.

Pro tip: If you get confused as to how all these functions interact, it's helpful to draw it out on a piece of paper. Check back to the Requirements section above for an overview.

Phew. You're done! Awesome job.

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Python Programming