IT 116: Introduction to Scripting

IT 116: Introduction to Scripting
Homework 11

Due
What You Need to Do
Setup On Your Machine
Specification
Functions
Test Code
Output
Suggestions
Testing on Your Machine
Copy the Script to Unix
Testing the Script on Unix (Optional)

Due

Sunday, November 24th at 11:59 PM

What You Need to Do

Create the script hw11.py
Make sure it obeys the rules in Rules for Homework Scripts
Make sure the script has a hashbang line and is executable
Move it to an an hw11 directory on pe15.cs.umb.edu

Setup On Your Machine

Open a text editor.
I would suggest the text editor built into the program IDLE.
Save the file as hw11.py
Copy the file numbs.txt from /home/ghoffman/course_files/it116_files.
Use FileZilla to do this.

Specification

This script will read in a file of numbers, one one to a line and convert it into a list
The file looks like this
```
46
19
35
43
...
```
It will then find the mean (average) and the median of the numbers in the list
The median is the value in the middle of a sorted list
It will do this by defining 3 functions
- read_file_into_integer_list
- list_mean
- list_median

Functions

read_file_into_integer_list

Header

def read_file_into_integer_list(filename):

The function should try to create a file object on a file whose name is contained in the parameter filename
This should be done inside a try/except statement
If the function cannot open the file, it should return an empty list
It should then read in each line using a for loop
Each line should be converted into an integer
And added to a list
This list is returned
The function should use the following algorithm

	create an empty list
	try:
	   create a file object for reading on filename
	   for each line in the file:
	      covert the line into an integer
	      append the integer to the list
	      return the list
	except:
	   return the empty list

list_mean

Header
```
def list_mean(list):
```
This function should use a for loop to total all the numbers in the list pointed to by the parameter list
It should calculate the average by dividing the total by the length of the list
And return the rounded average
The function should use the following algorithm

	set total to 0
	loop over the numbers in the list:
	   add each number total
	set average to the total divided by the length of the list
	return the rounded average

list_median

Header
```
def list_median(list):
```
This function should sort the list pointed to by the parameter list
And return the value in the middle of the list
The function should use the following algorithm

	sort the list
	set index to integer division of the length of the list by 2
	return index

Test Code

Your script must contain the following statements

numbers = read_file_into_integer_list("xxxxxxx")
print("numbers: ", numbers)
numbers = read_file_into_integer_list("numbs.txt")
print("numbers: ", numbers)
mean = list_mean(numbers)
print("mean:    ",mean)
median = list_median(numbers)
print("median:  ", median)

They should appear at the bottom of your script

Output

The output should look something like this

numbers:  []
numbers:  [46, 19, 35, 43, 35, 33, 42, 6, 25, 6, 19]
mean:     28
median:   33

Suggestions

Write this script in stages
Test your script at each step
Print the steps below
And check them off as you finish each one

Create the script file.
Add a hashbang line.
Run the script.
It should produce no output.
Fix any errors you find.
Create a function header for each of the four functions.
For the body of each function write pass.
Run the script.
Fix any errors you find.
Remove the pass statement from read_file_into_integer_list.
Add a statement that creates an empty list and assigns it to the variable list.
Within a try/except statement, create a file object on the file whose name is given by the parameter filename.
The except code block should return list.
Copy the test code to the bottom of your script.
Comment out all but the first two lines of the test code.
Run the script and fix any errors you find.
Add an else clause to the try/except statement.
Inside this clause write a for that will read each line in the file.
Inside the loop, print each line.
Uncomment the next line in the test code.
Run the script and fix any errors you find.
Remove the print statement.
Replace it with a statement that turns the line into an integer and assigns the value to the variable num.
Print num.
Run the script and fix any errors you find.
Remove the print statement.
Replace it with a statement that appends num to list.
Outside the loop, return list.
Uncomment the next line in the test code.
Run the script and fix any errors you find.
Remove the pass statement from list_mean.
Create the variable total and set it to 0.
Write a for loop over the list pointed to by the parameter list.
Name the loop variable num.
Inside the loop print num.
Uncomment the next line in the test code that calls list_mean.
Run the script and fix any errors you find.
Remove the print statement.
Replace it with a statement that adds num to total.
Outside the for loop print total.
Run the script and fix any errors you find.
Remove the print statement.
Replace it with a statement that sets the variable mean to total divided by the length of list.
Print mean.
Run the script and fix any errors you find.
Remove the print statement. Replace it with a statement that returns the rounded value of mean. Uncomment the next line in the test code.
Run the script and fix any errors you find.
Remove the pass statement from list_median.
Sort the list pointed to by the parameter list.
Create the variable index and assign it the value of the length of the list divided by 2 using integer division (//).
Return the value of the list element that has this index.
Run the script and fix any errors you find.

Testing on Your Machine

Open IDLE
Use the Open command in IDLE to open hw11.py
Run your script inside IDLE

Your output should look something like this

numbers:  []
numbers:  [46, 19, 35, 43, 35, 33, 42, 6, 25, 6, 19]
mean:     28
median:   33

Copy the Script to Unix

Open FileZilla and connect to pe15.cs.umb.edu
Go to your it116 directory
Go to your hw directory
Right-click in the whitespace inside the hw directory
Enter hw11 in the dialog box
Click and drag your script from the bottom left panel to the bottom right panel
Right-click on the file and select "Permissions" from the menu
Enter 755 in the box provided
This will make the script executable
Click and drag numbs.txt from the bottom left panel to the bottom right panel

Testing the Script on Unix (Optional)

Connect to pe15.cs.umb.edu using an ssh client like putty.exe (Windows) or ssh (Mac)
Go to the directory for this exercise
```
cd  it116/hw/hw11
```
Run this script
```
python3 hw11.py
```

You should see something like this

numbers:  []
numbers:  [46, 19, 35, 43, 35, 33, 42, 6, 25, 6, 19]
mean:     28
median:   33