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CPSC 115L: Introduction to Computing
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Fall 2010
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Homework 7
CPSC 115-01: due Monday, November 8
CPSC 115-02: due Tuesday, November 9
1. The class Time
First, download the file Time.py (for this, you
must be on this Homework 7 webpage and right-click the link provided). This
file contains a Python class named Time that represents the time of
day in the 24-hour notation. Save the file Time.py in a new folder
named hw7 inside your cpsc115 folder. To load the class
Time from the file Time.py into DrPython's interactive
session, type
>>> import os
>>> os.chdir('cpsc115/hw7')
>>> from Time import Time
1.1.
Open the file Time.py and study the class Time very
carefully. There are eight methods in this class. For the first two methods
__init__() and __str__(), docstrings concisely explain what
they do. What do the remaining six methods do? For each of these methods,
insert a docstring to explain what it does.
1.2.
In the class Time, implement a method named
to_seconds(self) that returns the time in seconds (i.e., the total
number of seconds elapsed since midnight). Your method should behave as
follows. Run your method with five test cases (including the one below) and
save the snapshots of your test runs in a text file named Time.out.
>>> time = Time(9, 23, 56)
>>> time.to_seconds()
33836
1.3.
In the class Time, implement a method named
from_seconds(self, seconds) that resets the time in the 24-hour
format with the value of seconds (which represents the total number
of seconds elapsed since midnight). Your method should behave as follows.
Run your method with five test cases (including the one below) and save the
snapshots of your test runs in the file Time.out.
>>> time = Time()
>>> time.from_seconds(33836)
>>> print time
09:23:56
1.4.
In the class Time, implement a method named
s_increment(self, seconds) that increments the time by the value of
seconds in seconds. Your method should behave as follows.
Run your method with five test cases (including the one below) and save the
snapshots of your test runs in the file Time.out.
>>> time = Time(9, 23, 56)
>>> time.increment(100)
>>> print time
09:25:36
1.5.
In the class Time, implement a method named
difference(self, another_time) that returns a Time object
that represents the time difference between the time and
another_time given as a Time object. Your method should
behave as follows. Run your method with five test cases (including the one
below) and save the snapshots of your test runs in the file
Time.out.
>>> start_time = Time(9, 23, 56)
>>> finish_time = Time(10, 54, 2)
>>> time_difference = start_time.difference(finish_time)
>>> print time_difference
01:30:06
2. What time will I get home?
Recall Exercise 4 (3) in Chapter 2 of Downey, which was assigned in
Homework 2. Now, using the class
Time, in the same file Time.py, implement a Python script to
solve the following generalization of this exercise: Given a start time and
the number of miles I will run at tempo, 7 minutes and 12 seconds per mile,
determine the time I will get home. As before, assume that I will run the
first and last miles at an easy pace of 8 minutes and 15 seconds per mile.
Your scrpit should behave as follows.
Enter the hour of the start time: 6
Enter the minute of the start time: 52
Enter the number of miles I will run at tempo: 2
If I start at 06:52:00 and run 2 miles at tempo, then I will be home at 07:22:54.
As usual, run your script with five test cases, and save the snapshots of your
test runs in the file Time.out.
What to hand in
Submit the following in paper. Be sure to put a file header at the top of
each file.
- Your Python script Time.py
- Your output file Time.out.
Plagiarism and academic dishonesty
Please remember our course policy on plagiarism and academic dishonesty:
You are encouraged to consult with one another when you work on homework
assignments, but in the end everyone must do one's own work to hand in. In
particular, discussion of homework assignments should be limited to
brainstorming and verbally going through strategies, but it must not involve
one student sharing written solutions with another student. In the end
everyone must write up solutions independently. If you have discussed
with classmates or used any outside source, you must clearly indicate so on
your solutions and provide all references. Turning in another person's work
under your name is plagiarism and qualifies as academic dishonesty. Academic
dishonesty is a serious intellectual violation, and the consequences can be
severe. For more details, read the
Student Handbook 2010–2011, pp. 21–29.
