Week 1, Problem 3: The Road Not Taken: Choosing Code Paths
[20 points; individual]

This problem asks you to write a Python function that test the use of the if elif and else constructs in python. Be sure to test your function carefully. Also, be sure to include a docstring under the signature line of the function. The docstring should indicate what the function computes (outputs) and what its inputs are or what they mean.

Please put your function for this problem in a single file named hw1pr3.py. Please name your function exactly as specified (including upper/lower case) -- it will help keep the graders happy -- which is always a good thing!

(#1) Building from last week's rock-paper-scissors game (which did not have to be fair), for this week, write a function rps() that plays a game of rock-paper-scissors fairly.

That is, it should first choose randomly from the three choices, though it should not reveal that choice! Then, the function should ask the user for her choice. Afterwards, it should print its original choice, the user's choice, and then declare the winner.

In addition, your rps function should print a warning if the user does not input one of 'rock', 'paper', or 'scissors'.

Choosing items at random from a sequence

To generate a random element from a list, model your code from the following example:

from random import *

s = choice( [ 'thread', 'yarn', 'twine' ])

print('I chose', s)

The above code will print a potentially different string each time it is run.

Print vs. return

Note that rps() takes no inputs and it has no return value -- it's a function that interacts with the user only via print and input statements. Thus, rps does not need to return anything. It is a good example of a function in which print is the desired means of interaction.

Playing again with while

Optionally, your function could use a while loop, in which it asks the user to play again and then continue (or not), based on their answer. This is not required, but if you'd like to do so, the following example shows how a while loop works:

answer = 'no'

while answer == 'no':

[body of the program]

answer = input('Would you like to stop? ')

Examples

Here are two separate example runs with the user's input in blue -- feel free to adjust the dialog for the sake of yourself (or the graders):

>>> rps( )

Welcome to RPS! I have made my choice.

Choose your poison: scissors

You chose scissors.

I chose rock.

I win!

And I didn't even cheat this time!

>>> rps( )

Welcome to RPS! I have made my choice.

Choose your poison: paper

You chose paper.

I chose rock.

You win!

I may have to reconsider my strategy in this game...

Submitting your file

You should submit your hw1pr3.py file at Canvas.

Next

Continue working on homework 1: hw1pr4

Homework 1