CSC111 Homework 9 2011

--D. Thiebaut 12:28, 13 November 2011 (EST)

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Problem #1

• Write a program called hw9a.py that outputs the average length of the presidency of US presidents, categorized by party. Your program should get the information from a file called presidents.txt, whose contents is available here.

If you are working on beowulf, you can get a copy of the file into your account this way:

 getcopy presidents.txt

Note that this file does not have triple double-quotes around the list of presidents, and that it does have a header, i.e. the first line defines what the different fields are, but is not a valid president line.

• You will get the contents of the file using a statement of the form

  file = open( "presidents.txt", "r" )

Requirements

• Your program should use functions. Study Homework 7 a second time to get inspiration for your program organization.
• Your program will assume that if a president is incumbent, his time is the current year (2011) minus the time he came to office. So, for Obama, this would be 2011-2009 = 2 years. Don't use the number 2. Make your program compute the current year minus whatever the year in office is. This way your program can work for future presidents.
• To get the current year in Python, you need to import the datetime module, as illustrated below. now.year is an integer.

import datetime
now = datetime.datetime.now()
currentYear = now.year 
print( "The current year is", currentYear )

• The output of your program should be only a few lines long. We do not want to see the list of presidents, but just something like this:

Average length of presidency.
File presidents.txt contains 44 presidents.
Democratic presidents: x.xx years
Republican presidents: x.xx years
Others: x.xx years

• The number of presidents (44) should be the number found by your program in the text file. When I test your program, I may provide a presidents.txt file with fewer than 44 presidents. Or a file that has just a header and no presidents at all! Or even a file with nothing in it, just empty. Be sure you test your program well so that it doesn't crash on any of these potential input files.

Submission

• Submit your program as follows:

rsubmit hw9 hw9a.py

if you worked on beowulf, or submit your program using this page: http://cs.smith.edu/~111a/submit9.htm

Problem #2

JT 150
TJ 80
TT 120
BT 170
Mike 12
AF 27
Lea 78
Leo 180
AI 55
GK 110

• We have a text file called people.txt, and this file contains lines of text, as illustrated above.
• Each line represents a person. The first string is that person's name (or initials), followed by a space, followed by a number representing that person's weight, in pounds. Any other line that doesn't follow this format is invalid.

• This list is actually the list of the first people who have signed up to use Google's first elevator to the moon when it becomes available (Check this NYT article to see what Google X is up to!)

• The only problem is that there is a maximum weight allowed, and that we may have to prevent some people from boarding. The maximum weight allowed is input by the user, as illustrated below:

>>> 
Google X Elevator
Candidates for first boarding of elevator:
        JT (150 lbs)
       TJ (80 lbs)
       TT (120 lbs)
       BT (170 lbs)
     Mike (12 lbs)
       AF (27 lbs)
      Lea (78 lbs)
      Leo (180 lbs)
       AI (55 lbs)
       GK (110 lbs)

Max weight? 2 hundred
Invalid weight.  Please try again.
Max weight? infinite
Invalid weight.  Please try again.
Max weight? 200
4 people can board the elevator
Their combined weight is 172
The selected group includes:  AF, AI, Lea, Mike
The rejected group includes:  BT, GK, JT, Leo, TJ, TT

• Our only criterion for boarding the elevator will be their weight.

Write a program called hw9b.py that will compute and output the answers to the following questions:

Question 1

What is the maximum number of people that can fit in the elevator?

Question 2

What is the total weight of the people who fit in the elevator?

Question 3

What are the names of the people in the elevator?

Question 4

What are the names of the people who will have to wait and go in the second batch?

• Use while or for loops, as you see fit.

• Make sure your program is robust! (It could be that the file does not exist, of that the person's name is several words long. It is also possible that the weight is a real number, e.g. 180.5)

• Once your program works, modify it and make it input the total weight allowed in the elevator from the user. The allowed range allowed by your program should be any number between 0 and 1000. If the number entered by the user is less than 0 or greater than 1000, your program should prompt the user to input that number again.

• Make sure your program works if the maximum weight allowed is 0, or when it is set to 1000.