IT 117: Intermediate Scripting

IT 117: Intermediate Scripting
Homework 3

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 16th at 11:59 PM

What You Need to Do

Create the script hw3.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 hw3 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 hw3.py
Copy the file classs.txt from /home/ghoffman/class_files/it117_files to the same directory as your script.
Use FileZilla to do this.

Specification

This script reads in class data from a file
It uses this data to create a class dictionary
And then prints the dictionary
The script must contain 3 functions
- open_file_read
- class_dictionary_create
- print_classes

Functions

open_file_read

Header
```
def open_file_read(filename):
```
The function will try to create a file object using the parameter filename
This should be done inside a try/except statement
If the object is created it should be returned
If a file object cannot be created the function should print an error message

class_dictionary_create

Header
```
def class_dictionary_create(file):
```
The function reads in a file with four fields of data about a class on a single line
These fields are
- class ID
- Room Number
- Instructor
- Start Time

The file looks like this:

CS101 3004 Haynes 8:00
CS102 4501 Smith 9:00
CS103 6755 Rich	10:00
NT110 1244 Burke 11:00
CM241 1411 Lee 13:00

The function should read in each line of the file and split it into a list of 4 elements
It should use this list to create a dictionary where the class_id is the key ...
and the value is a tuple consisting of the room number, the instructor and the start time
The function should return this dictionary

The function should use the following algorithm

create the empty dictionary class_dict
loop through the file
	create the list fields by running split on each line
	set the variable class_id to the fields entry with index 0
	set the variable room to the fields entry with index 1
	set the variable instr to the fields entry with index 2
	set the variable start to the fields entry with index 3
	create the tuple class_data using the variables room, instr and start
	make an entry in class_dict with class_id as the key and class_data as the value
return class_dict

print_classes

Header
```
def print_classes(class_dict):
```
The function should print a table header listing each field
Followed by a line of dshes
It should the print the data for each class ...
in alpabetical order by class_id
Each label should be vertically aligned with the data below
To see what I mean, see the Output section below

Test Code

Your script must contain the following statements

They should appear at the bottom of your script

open_file_read("xxxxx")
file = open_file_read("classes.txt")
class_dictionary = class_dictionary_create(file)
print_classes(class_dictionary)

This code will only work if you have copied classs.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

Cannot open xxxxx
ID      Room	Instr	Start
-----------------------------------
CM241	1411	Lee     13:00
CS101	3004	Haynes	8:00
CS102	4501	Smith	9:00
CS103	6755	Rich	10:00
NT110	1244	Burke	11:00

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 hw3.py
Copy the function headers for open_file_read, class_dictionary_create and print_classes into it.
For the body of each function enter pass.
Make the script executable and run it.
You should see nothing.
If you get an error message, fix the problem before proceeding.
Remove the pass statement from open_file_read.
In its place write a try/except statement.
The try block should contain code to create a file object for reading using the using the filename parameter.
Under this statement return the file object.
In the except clause print an error message.
Copy the text code to the bottom of the file.
Comment out the last two lines.
Run the script.
You should see
```
Cannot open xxxxx
```
Remove the pass statement from class_dictionary_create.
Create the empty dictionary class_dict.
Write a for loop that prints each line in the file.
Remove the comment from the 3rd line in the test code.
Run the script and fix any errors find.
Remove the print statement you just created.
In it's place set the variable fields to what you get when you call split on the line.
Print fields.
Run the script and fix any errors.
Remove the print statement you just created.
Define the variable class_id and set its value to the first element of the list fields.
Print the value of class_id.
Run the script and fix any errors.
Remove the print statement.
Create the variables room, instr and start from fields using an appropriate index for each.
Create the variable class_data and set its value to a tuple consisting of three variables defined above.
To create a this tuple, put parentheses ( ) around these variables.
Print class_id and class_data.
Run the script and fix any errors.
Remove the print statement you created above.
Replace it with a statement that creates an entry in the dictionary class_dict.
Use class_id as the key and class_data as the value.
Outside the loop but still inside the function, print this dictionary.
Run the script and fix any errors.
Remove the print statement from class_dictionary_create.
Replace it with a statement that returns the dictionary class_dict.
Remove the pass statement from print_classes and replace it with a statement that prints the parameter class_dict.
Uncomment the last line in the test code.
Run the script and fix any errors.
Write a for loop on the sorted dictionary class_info using class_id as the loop variable.
Inside the loop print class_id.
Run the script and fix any errors.
Remove the print statement.
Replace it with a statement that creates the variable class_data from the value in the dictionary specified by the key class_id.
Print class_id and class_data.
Run the script and fix any errors.
Change the print statement so that it prints the class_id and each element of the tuple with a Tab, \t, between each value.
You will have to do this using concatenation.
Run the script and fix any errors.
Write a print statement before the for loop that print labels for each column.
Use tabs, \t, to separate each label so it lines up with each value printed in the for loop.
Write another print statement to produce a line of dashes.

Testing on Your Machine

Open IDLE.
Use the Open command in IDLE to open hw3.py
Run your script inside IDLE

Your output should look something like this

Cannot open xxxxx
ID      Room	Instr	Start
-----------------------------------
CM241	1411	Lee     13:00
CS101	3004	Haynes	8:00
CS102	4501	Smith	9:00
CS103	6755	Rich	10:00
NT110	1244	Burke	11:00

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 hw3 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 classs.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/hw3
```
Run this script
```
python3 hw3.py
```

You should see something like this

Error: Unable to open xxxxx
ID      Room    Instr   Start
-------------------------------
CM241   1411    Lee 	13:00
CS101   3004    Haynes  8:00
CS102   4501    Smith   9:00
CS103   6755    Rich    10:00
NT110   1244    Burke   11:00