IT 117: Intermediate Scripting

IT 117: Introduction to Scripting
Homework 6

Due

Sunday, March 3rd at 11:59 PM

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

What You Need to Do

Create the script hw6.py
Make sure it obeys the rules in Rules for Homework Scripts
Move it to an an hw6 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 hw6.py

Specification

This script must have 4 functions
- script_filename
- system_var
- count_files
- executable_files_dictionary
This script can ONLY be tested on pe15.cs.umb.edu

The script must have 4 functions:

Functions

script_filename

Header
```
def script_filename():
```
This function returns the filename of the script hw6.py
It uses argv from the sys module

system_var

Header
```
def system_var(var):
```
This function returns the value of the system variable given by the parameter var

count_files

Header
```
def count_files(path):
```
This function goes to the directory specified by the parameter path
It then counts all the files (not directories) in that directory and returns that count
The function should use the following algorithm.

	go to the directory indicated by path
	initialize count to 0
	create the list entries of all items in the directory 
	for each  entry in the list entries
	   if entry is a file
	      increment count 
	return count

executable_files_dictionary

Header
```
def executable_files_dictionary(path):
```
This function goes to the directory specified by the parameter path
It looks for files with extensions "pl", "py" or "sh" and returns a dictionary with the filename of each file with that extension
The key of this dictionary is the extension and the value is a list of files with that extension
The function should use the following algorithm

	go to the directory indicated by path
	create the empty dictionary files_dict
	create the list entries of all items in the directory
	for each  entry in the list entries
	   if  entry is a file
	      run split on entry to get values for name and ext
	      if ext is contained in the list EXECUTABLE_EXT
	         if ext is NOT in files_dict
	            create the list new_list with a name as its only entry
	            create a new entry in files_dict with key ext and value new_list         
	         else       
	            get the value in files_dict associated with ext and assignment it to files_list
	            append name to files_list
	            set the value associated with ext in files_dict to files_list
	return files_dict

Test Code

Your script must have the following test code at the bottom of the script

FILES_DIR      = "/home/ghoffman/course_files/it117_files/misc_scripts"
EXECUTABLE_EXT = ["pl", "py", "sh"]
print(script_filename())
print(system_var("SHELL"))
print(count_files(FILES_DIR))
files_dictionary = executable_files_dictionary(FILES_DIR)
for ext in sorted(files_dictionary):
    print(ext, files_dictionary[ext])

The test code above will looks for the system variable SHELL and the directory /home/ghoffman/course_files/it117_files/misc_scripts
It will ONLY work on pe15.cs.umb.edu
Yoy may work on the code on your own machine
But you must move it to pe15.cs.umb.edu to test it

Output

Your output should look like this

$ ./hw6.py 
hw06.py
/bin/bash
9
pl ['perl_evens.pl']
py ['semester.py', 'regex_test_with_group.py', 'regex_test.py']
sh ['admin_commit.sh', 'advising_log_prune.sh', 'attendance_commit.sh']

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 hw6.py.
Import the os and sys modules.
Write the headers for all the specified functions specified above.
Under each header write the Python statement pass.
Run the script.
Fix any errors you find.
Remove the pass statement from script_filename.
In its place write a statement to return the value of sys.argv.
Copy the test code to the bottom of the script.
Comment out all but the first 3 lines.
Run the script.
You should see
```
['./hw6.py']
```
Fix any errors you find.
Change the return statement so it only returns the first value in the list.
Run the script.
You should see
```
./hw6.py
```
Fix any errors you find.
There is a function in the os module that, when run on a pathname, returns only the filename.
Apply that function to the first value in the list.
Run the script.
You should see
```
hw6.py
```
Fix any errors you find.
Remove the pass statement from system_var.
There is a dictionary in the os module, where system variables are the key and the value is the value of the system variable.
Use that dictionary to return the value of the system variable contained in the parameter var.
Uncomment the next line in the test code.
Run the script.
Fix any errors you find.
Remove the pass statement from count_files.
Replace it with a statement that goes to the directory specified in the parameter path.
Initialize the variable count to 0.
There is an os module function that creates a list of entries in a directory.
Use this function to create the list entries.
Return entries.
Uncomment the next line in the test code.
Run the script.
Fix any errors you find.
Remove the return statement.
Write a for loop with loop variable entry over the list entries.
Inside the loop, print entry.
Run the script.
It should list and the files witn "None" at the end.
Fix any errors you find.
Remove the print statement.
There is an os module function that returns True if its argument is a file.
Use this function in an if statement that works if entry is a file.
Inside the if statement, print entry.
Run the script.
Fix any errors you find.
Remove the print statement.
Replace it with a statement that increments count.
Outside the for loop, return count.
Run the script.
Fix any errors you find.
Remove the pass statement from executable_files_dictionary.
Replace it with a statement that goes to the directory specified in the parameter path.
Create an empty dictionary called files_dict.
Uncomment the next line in the test code.
Run the script.
You should not see any change in the output.
Fix any errors you find.
Create the list entries containing everything in the current directory.
Write a for loop over entries using the loop variable entry.
Inside the loop, print entry.
Run the script.
Fix any errors you find.
Remove the print statement.
Write an if statement that works if entry is a file.
Print entry inside the if statement.
Run the script.
Fix any errors you find.
Remove the print statement.
Using split on entry with an argument of ".", assign values to the variables name and ext.
For an example of what I mean, see Class Exercise 3.
Print the values of name and ext.
Run the script.
Fix any errors you find.
Remove the print statement.
Write an if statement that works if ext is in the list EXECUTABLE_EXT.
Inside the if statement, print entry.
Run the script.
Fix any errors you find.
Remove the print statement.
Write an if statement that works if ext is not already in the dictionary files_dict.
Inside this if statement create the list new_list whose only element is entry.
Make a new entry in files_dict using ext as the key and new_list as the value.
Outside the for loop return files_dict.
Uncomment the last two lines of the test code.
Run the script.
You should see
```
pl ['perl_evens.pl']
py ['semester.py']
sh ['advising_log_prune.sh']
```
Fix any errors you find.
Add an else clause to the if statement you created above.
Inside the else clause assign the current value associated with the key ext to the variable files_list.
Append entry to files_list.
Change the entry in files_dict associated with ext to files_list.
Run the script.
You should see
```
pl ['perl_evens.pl']
py ['semester.py', 'regex_test_with_group.py', 'regex_test.py']
sh ['advising_log_prune.sh', 'attendance_commit.sh', 'admin_commit.sh']h
```
Fix any errors you find.

Testing the Script on Unix

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/hw6
```
Run this script
```
./hw6.py
```

You should see

hw6.py
/bin/bash
9
pl ['perl_evens.pl']
py ['semester.py', 'regex_test_with_group.py', 'regex_test.py']
sh ['admin_commit.sh', 'advising_log_prune.sh', 'attendance_commit.sh']