HW 9 (Lunar Lander Part 1)

Practice using object-oriented programming.

This is a partner assignment, which means you should complete all pieces of this assignment with your assigned partner. In particular, any coding must be completed side-by-side in a pair programming style. You are welcome to discuss the assignment with other classmates, course staff or Anna. Make sure to cite any help you receive in the "acknowlegdements" portion of the assignment.

There are new partnerships for this assignment. Check Moodle to see who you're working with.

This assignment is due at 10PM on Wednesday, May 20.

• interfaces.py contains two classes. For this assignment, you'll use (and minimally edit) the TextLanderInterface class. Take some time to read through this class and its methods.
• graphics.py won't be used until HW10 (Lunar Lander Part 2).

You should create a third file, lunarLander.py in your hw9 directory. Almost all of your code will be written to this file.

First, you'll write a class caled LunarLander (in Python, the names of classes traditionally start with a capital letter). This class will represent the spacecraft.

You'll need to create several instance variables and methods for this class.

Instance variables you need include altitude (how far the spacecraft is above the surface of the moon), velocity (how fast the ship is moving. A negative velocity means that the spacecraft is moving towards the moon, while a positive velocity means its moving away from the moon's surface and further into space), and fuel (how much fuel is left in the tank).

Methods you need include:

• A constructor, that takes in the parameters necessary to create a LunarLander object.
• getAltitude, a method that takes no parameters other than self and returns the numeric (integer) altitude of the lander. Positive numbers indicate higher in the sky, while 0 indicates you are on the moon's surface.
• getVelocity, a method that takes no parameters other than self and returns the current velocity of the moon lander.
• getFuel, a method that takes no parameters other than self and returns the amount of fuel currently in the tank.
• update, a method that takes the parameters self and thurstAmount, an integer indicating how much thrust to apply to the ship. update will update the lander's altitude and velocity in accordance with how much thrust was applied. Specifically, you should
  • Use thrustAmount units of fuel if possible (if not enough fuel is available, just use what is left)
  • For each unit of fuel that is burnt, increase the ship's velocity by 2.
  • Subtract 1 from the velocity to account for gravity (remember, positive velocity means the spacecraft is traveling away from the moon and negative velocity means it's going towards the moon).
  • Compute and set the new altitude, calculated as the old altitude plus the new velocity. If this value is less than or equal to 0, the spacecraft has reached the moon (either a successful landing or a crash) in which case you should set the altitude to 0.

To actually play our game, we need a class that will handle game play: it'll create the lunar lander object and then repeatedly ask the user for how much thrust to use, while updating the lander's instance variables to keep track of altitude, fuel, velocity, and whether it has landed.

Create a class LanderGame in lunarLander.py. For now, this class will have a constructor and one other method, play. The constructor should create two instance variables, lander and interface. lander is an instance of the LunarLander class and should be initialized to have velocity 0, altitude 100, and fuel 30. interface will (for this assignment) be a TextLanderInterface object. You'll need to import the interfaces module at the top of your file – be cognizant of how you import the module and how you'll have to initialize objects from this module.

The play method will handling playing the game. It should keep asking the user for information (how much thrust to use) until the lunar lander lands safely or crashes. play should do the following tasks:

• Normal game play: do the following in a loop as long as the lander instance variable has altitude above 0.

  • Ask the interface object to show the current status of the lander (altitude, velocity, fuel). Do not write your own code to do this. Use the methods in TextLanderInterface.
  • Ask the interface to get a thrust amount from the user. Again, don't write your own code to do this: use the methods in TextLanderInterface.
  • Update the lunar lander's information with the returned amount.
• Handling ground contact: when the lander's altitude reaches 0, check its velocity. If its velocity is less than -5, it has crashed. Otherwise, it has landed safely.
• Display results to the user: Based on whether it was a successful landing or a crash, display the correct error message to the user. Don't write your own code to do this; use the methods in TextLanderInterface.
• Close the interface: call the interface's close() method to exit.

Add a main function to lunarLander.py that will create a LanderGame instance and call its play method to play the game. Here's a sample run of what playing the game should look like, if the player always chooses 0 thrust:

Lander Status: Altitude 100, Velocity 0, Fuel 15
Thrust amount? 0
Lander Status: Altitude 99, Velocity -1, Fuel 15
Thrust amount? 0
Lander Status: Altitude 97, Velocity -2, Fuel 15
Thrust amount? 0
Lander Status: Altitude 94, Velocity -3, Fuel 15
Thrust amount? 0
Lander Status: Altitude 90, Velocity -4, Fuel 15
Thrust amount? 0
Lander Status: Altitude 85, Velocity -5, Fuel 15
Thrust amount? 0
Lander Status: Altitude 79, Velocity -6, Fuel 15
Thrust amount? 0
Lander Status: Altitude 72, Velocity -7, Fuel 15
Thrust amount? 0
Lander Status: Altitude 64, Velocity -8, Fuel 15
Thrust amount? 0
Lander Status: Altitude 55, Velocity -9, Fuel 15
Thrust amount? 0
Lander Status: Altitude 45, Velocity -10, Fuel 15
Thrust amount? 0
Lander Status: Altitude 34, Velocity -11, Fuel 15
Thrust amount? 0
Lander Status: Altitude 22, Velocity -12, Fuel 15
Thrust amount? 0
Lander Status: Altitude 9, Velocity -13, Fuel 15
Thrust amount? 0
Crash! Oh no!
Goodbye

Make sure to also add the if name == "__main__" block so that you can play your game by running python3 lunarLander.py from the terminal.

You need to hand in lunarLander.py and interface.py on Gradescope. Only one partner should submit the assignment to Gradescope (but make sure to add your partner to your group after submitting).

This assignment is worth 30 points, broken up as follows:

• 10 points LunarLander class
• 10 points LanderGame class
• 5 points Improvements
• 5 points style (reflections, acknowledgments, comments, coding style)

Start early, ask lots of questions, and have fun!