Lab 7: Strings

CSCI 141 
Lab 7: Strings
Introduction
In this lab you’ll gain practice using and manipulating strings. In lecture you’ve seen how to
iterate over the characters in a string, access individual characters by index, and how to slice
out substrings. We also touched on a few of the multitude of methods that can be called on
string objects, including upper, lower, find, and replace.
Suppose you are an employee at a software company called Lotter.io. You have been tasked
with writing a Python program that will simulate the drawing of a winning lottery pick, then
prompt a user to guess the lottery pick, and inform the user if their pick is the winning pick.
Your company’s secret sauce that will guarantee its explosive growth into a billion dollar startup
is that the lottery doesn’t just involve guessing numbers: Instead, this lottery involves both
words and digits. A lottery pick is made up of one of three words (monkey, dragon, or snake),
and one of three digits (1, 2 or 3), arranged either with the word first or the number first. For
example, monkey1, and 2dragon are both possible winning picks. The user only wins if the
correct word and the correct digit are guessed in the correct order.
The program consists of three main tasks:
1. Generate a winning pick.
2. Get a valid pick from the user.
3. Check the user’s pick against the winning pick and tell them how they did.
Three sample invocations are shown in Figure 1.
1 Generate a winning pick
Random pick generation is to be implemented in the generate winner function. The function
header, specification, and some of its implementation have been written for you.
Easter Egg
Our lottery game will have a secret easter egg, a hidden feature that’s only accessible to those
who have read the code, or users who somehow stumble upon it. Our easter egg behavior is as
follows.
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Figure 1: Three sample invocations
The welcome message tells the user to press enter to continue; however, if the user enters
something that looks like a valid pick and then presses enter, generate winner will simply use
their input as the correct pick.
The functionality for this easter egg has been implemented for you: the begin input variable
captures what the user enters, and is passed into the generate winner function, which first
checks to see if it should return the cheat pick. This “cheater mode” may help you more
thoroughly test your program’s behavior by giving you the option to choose the winning pick
without any randomness involved. It will also make grading easier for us, for the same reasons,
so be sure not to modify the code that implements this feature.
Your task is to write the code after this part of the function that generates and
returns a truly random winning pick. Pseudocode for your portion of the function is
provided as comments in the skeleton code.
2 Get a valid pick from the user.
Implement the get_valid_guess function to prompt the user, repeatedly if necessary, until
they enter a guess that contains one of the words and begins or ends with one of the numbers.
Notice that these criteria do make it possible to enter an invalid pick (e.g., dragoncat3 contains
one of the words and ends with one of the numbers. This is fine: cases such as these will be
handled later in the program. The function header, specification, and pseudocode for this part
are provided in the skeleton code.
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3 Check the user’s pick
Now, we need to tell the user whether any or all aspects of their pick were correct. Here’s
what the program should do once it has determined the winning pick and the user’s pick. Your
messages do not need to match mine exactly, but should convey the same content. Feel free to
decide on your own prize for guessing the winning pick.
• If the user inputs a pick that exactly matches the winning pick character for character,
the program outputs a message telling the user they’ve won.
• If the user’s word and number both match the winning pick, but their pick doesn’t match
the winning pick exactly, print You guessed the correct number and word in the wrong
order!
• If the number matches but the word doesn’t, print You guessed the correct number but
not the correct word.
• If the word matches but the digit isn’t correct: print You guessed the correct word but not
the correct number.
• If neither the word nor number are correct, print You guessed neither the correct word
nor the correct number.
The main method includes calls to the two functions you completed in the prior tasks, followed
by pseudocode for this step. You may want to, but are not required to, create a separate
function to accomplish this task.
Getting Started
Download the skeleton code lottery.py from the course webpage. Open up and read through
the skeleton code, making sure that you understand the provided code and function specifications. We recommend completing the three tasks in the order described above.
You may find the in and not in operators useful on strings, as well as indexing individual
characters of a string and slicing substrings. Review the lecture slides for details on the syntax
for these operators. Don’t forget that when a program’s logic gets complicated, it can be helpful
to define boolean variables to keep the conditions of if/elif statements short and easy to read.
Submission
Submit your completed program lottery.py file via Canvas.
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Rubric
Submitted a file called lottery.py 1
Comment at the top of program specifies author, date, and description 1
Easter egg code is unmodified 1
Random pick is generated 5
User is prompted again if guess doesn’t contain one of the words 5
User is prompted again if guess doesn’t begin or end with one of the numbers 5
Message printed for correct pick 5
Message printed for correct word and number but incorrect order 5
Message printed for correct word but not number, and vice versa 5
Message printed for neither correct 5
Coding style (commenting, variable names, etc.) 2
Total 40 points
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