Overview

• Gain familiarity with working with conditionals
• Become familiar with using the mod operator
• Understand using conditionals to manage errors and special cases

Step 0: Setup

The first step is to create a lab4 folder in your cs201/labs directory and make a lab4.py file to start programming.

From your home directory :

cd 201/labs
mkdir lab4
cd lab4
emacs lab4.py &

Step 1 - What's a perfect number ?

Your task for lab 4 is to write a program that determines whether a number the user enters is a perfect number or not.

A perfect number is a positive integer that is equal to the sum of its divisors (excluding itself).
For example, the divisors of 6 are 1, 2 and 3. Since 6 = 1 + 2 + 3, 6 is a perfect number. The next three perfect numbers are 28, 496 and 8128.

Step 2 - How do I do that ?

• Your task for lab4 is to write a program that takes a positive integer from the user as input and prints whether it is a perfect number or not.
• If the user enters a negative number, or a floating point number, you should not continue and inform the user the number needs to be a positive integer.
• You should loop through all integers less than the input integer, and add them together if they are divisors of the input integer.
• To loop through all integers less than the integer <number> you use the following format:

for i in range(1, number):
	#do something with i

• The modulus operator in python is the percent symbol '%'.
• The modulus of two numbers A % B is the remainder after dividing A by B.

>>> 5 % 1
0
>>> 5 % 2
1
>>> 5 % 3
2
>>> 5 % 4
1

• This means that if B is a divisor of A then A % B is equal to 0.

Bonus Step - Eligibility

Use emacs to write bonus4.py that performs the following eligibility tests and prints out a report that states what things the user is eligible for and if they're not eligible for something, why not.

1. For the Lab 4 bonus, you will prompt a user for information and tell them how eligible they are to smoke, drink alcohol, rent a car in Maryland, vote in Maryland, be a US senator, and be President of the United States
2. To start you will prompt the user for the following information
   • Age
   • Length of time as a US citizen
   • Whether the user was born in the US
   • Length of time living in the US
   • How many times the user has been convicted a felony
3. Based on the input information, the program should tell the user whether they are eligible for each of the criteria, and if not, why not.
   • To be able to smoke tobacco, the user must be >=18 years old.
   • To be able to drink alcohol, the user must be >=21 years old.
   • To be able to rent a car in Maryland, the user must be >=25 years old.
   • To be able to vote in Maryland, the user must be >= 18 years old, and have not been convicted of a felony more than once.
   • To be a US senator the user must be >= 30 years old, and have been a citizen for at least 9 years.
   • To be the President of the United States the user must be >=35 years old, was born in the US, and have lived in the US for at least 14 years.

Challenge Step - Security Clearance

Make a copy of your bonus4.py file called challenge4.py and modify the new file to include the eligibility for security clearance.

• Add the following questions for the user to answer.
  • Whether the user is dating or is married to someone who is a foreign national
  • Whether the user has much financial debt (standard things like student loans may be ignored)
  • Whether the user has any DUIs
  • Whether the user has used illegal drugs, and if so how many years ago (0 if less than a year)
• For security clearance, exceptions can always be made, so the following is a point-based heursitic for how difficult it would be to obtain security clearance.
• The point system for security clearance is as follows :
  • Lack of citizenship awards 5 points.
  • Not being born in the US awards 2 points.
  • Dating or being Married to a foreign national awards 2 points.
  • Drugs : A user receives :
    4 points for using illegal drugs less than a year ago
    2 points if greater than one, but less than two years ago
    1 point for greater than two, but less than three years ago
    no points for greater than three years ago
  • A user gets 6 points if they've been convicted of any felonies
  • A user receives 3 points if they have any DUIs
  • A user receives 6 points if they are not at least 18 years old
• If the user has 0 points, getting security clearance should be trivial
• If the user has 1-3 points the user may have some difficulty getting security clearance
• If the user had 4-5 points, it will be very hard for the user to get security clearance
• If the user has >=6 points it will be next to impossible for the user to get security clearance