IT 117: Intermediate Scripting

IT 117: Introduction to Scripting
Homework 2

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, February 8th at 11:59 PM

What You Need to Do

Create the script hw2.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 hw2 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 hw2.py
Copy the file qz_04_grades.txt from /home/ghoffman/course_files/it117_files.
Use FileZilla to do this.

Specification

Your script must read a file with lines like this
```
95	Alan Ball
98	Eddie Bauer
80	Dan Franks
...
```
It must find the lowest score in this file and print the score along with the name of the student who got the score
The script must contain 2 functions
- open_file_read
- lowest_score

Functions

open_file_read

Header
```
def open_file_read(filename):
```
It must try to create a file object for reading on the file whose name is given by the parameter filename
If it can create the file object it should return it
If it is cannot create the object it should print an error message and return None

lowest_score

Header
```
def lowest_score(file):
```
This function takes one parameter, file, a file object for reading
The function should loop through the file looking for the lowest score and the name of the student with that score
The function must return the lowest score and the name of the student who earned that score
The function should use the following algorithm

	set min_score to 500
	set min_name  to the empty string
	for each line in the file:
		split the line into three values score first and last
		concatenate first, a space and last and assign it to name
		turn score into an integer
		if score is less than min_score:
			replace min_score with score
			replace min_name with name
	return min_score and min_name

Test Code

Your script must contain the following statements

filename = input("File name: ")
file = open_file_read(filename)
if file:
    min_score, min_name = lowest_score(file)
    print()
    print("Lowest score", min_score, min_name)

They should appear at the bottom of your script
This code will only work if you have copied qz_04_grades.txt into the same directory as your script
You will find this file in /home/ghoffman/course_files/it117_files

Output

The output should look something like this

File name: qz_04_grades.txt

Lowest score 45 Joseph Sanders

The text in blue is what the user enters

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 file hw2.py.
Enter the headers for open_file_read and lowest_score.
Under each header write the Python statement pass.
Run the script.
Fix any errors you find.
Replace the pass statement in open_file_read with a try/except statement.
Inside the try block write a statement that creates a file object for reading.
Then return the file object.
Inside the except block write a statement that prints an error message.
Then return None.
Copy the test code to the bottom of the file.
Comment out all but the first two lines of the test code.
Run the script entering both a real filename and the name of a file that does not exists.
Fix any errors you find.
Remove the pass statement from lowest_score.
Write an assignment statement that sets min_score to 500.
Write another assignment statement that sets min_name to the empty string.
Write a for loop that prints each line in the file.
After the for loop and outside it, return two empty strings.
You need to do this to avoid a syntax error when run the test code.
Uncomment the last three lines of the test code to the bottom of the file.
Run the script entering qz_04_grades.txt when prompted.
Fix any errors you find.
After the print statement in lowest_score, write an assignment statement with the variables score, first and last on the left side and a call to split on the variable holding the line.
For an example of what I mean, see Class Exercise 3.
Print the three new variables.
Run the script.
Fix any error you find.
Remove the statement that prints the line.
Create the variable name by concatenating first and last with a space in between.
Write an assignment statement that converts score to an integer.
Change the remaining print statement by replacing first and last with name.
Run the script.
Fix any error you find.
After the statement that converts score to an integer, write an if statement that will will run if the value of score is less than min_score.
If it is, set min_score to the value of score and min_name gets the value of name.
If you are not sure what I mean see this Class Exercise from IT 116.
Run the script.
Fix any error you find.
Remove the print statement from inside the for.
Run the script.
Fix any error you find.

Testing on Your Machine

Open IDLE
Use the Open command in IDLE to open hw2.py
Under the Run menu, select Run Module

Your output should look something like this

File name: qz_04_grades.txt

Lowest score 45 Joseph Sanders

The text in blue is what the user enters

Copy the Script to Unix

Open FileZilla and connect to pe15.cs.umb.edu
Go to your it117 directory
Go to your hw directory
Right-click in the whitespace inside the hw directory
Enter hw2 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 qz_04_grades.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  it117/hw/hw2
```
Run this script
```
./hw2.py
```
You should see something like this
```
Lowest score 45 Joseph Sanders
```