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Home | Lecture 6 | Problem 6.1 | Problem 6.2 | Problem 6.3 | Problem 6.4

Scourgify

Ah, well,” said Tonks, slamming the trunk’s lid shut, “at least > it’s all in. That could do with a bit of cleaning, too.” She pointed her wand at Hedwig’s cage. “Scourgify.” A few feathers and droppings vanished.
— Harry Potter and the Order of the Phoenix

Data, too, often needs to be “cleaned,” as by reformatting it, so that values are in a consistent, if not more convenient, format. Consider, for instance, this CSV file of students, before.csv, below:

	name,house
	"Abbott, Hannah",Hufflepuff
	"Bell, Katie",Gryffindor
	"Bones, Susan",Hufflepuff
	"Boot, Terry",Ravenclaw
	"Brown, Lavender",Gryffindor
	"Bulstrode, Millicent",Slytherin
	"Chang, Cho",Ravenclaw
	"Clearwater, Penelope",Ravenclaw
	"Crabbe, Vincent",Slytherin
	"Creevey, Colin",Gryffindor
	"Creevey, Dennis",Gryffindor
	"Diggory, Cedric",Hufflepuff
	"Edgecombe, Marietta",Ravenclaw
	"Finch-Fletchley, Justin",Hufflepuff
	"Finnigan, Seamus",Gryffindor
	"Goldstein, Anthony",Ravenclaw
	"Goyle, Gregory",Slytherin
	"Granger, Hermione",Gryffindor
	"Johnson, Angelina",Gryffindor
	"Jordan, Lee",Gryffindor
	"Longbottom, Neville",Gryffindor
	"Lovegood, Luna",Ravenclaw
	"Lupin, Remus",Gryffindor
	"Malfoy, Draco",Slytherin
	"Malfoy, Scorpius",Slytherin
	"Macmillan, Ernie",Hufflepuff
	"McGonagall, Minerva",Gryffindor
	"Midgen, Eloise",Gryffindor
	"McLaggen, Cormac",Gryffindor
	"Montague, Graham",Slytherin
	"Nott, Theodore",Slytherin
	"Parkinson, Pansy",Slytherin
	"Patil, Padma",Gryffindor
	"Patil, Parvati",Gryffindor
	"Potter, Harry",Gryffindor
	"Riddle, Tom",Slytherin
	"Robins, Demelza",Gryffindor
	"Scamander, Newt",Hufflepuff
	"Slughorn, Horace",Slytherin
	"Smith, Zacharias",Hufflepuff
	"Snape, Severus",Slytherin
	"Spinnet, Alicia",Gryffindor
	"Sprout, Pomona",Hufflepuff
	"Thomas, Dean",Gryffindor
	"Vane, Romilda",Gryffindor
	"Warren, Myrtle",Ravenclaw
	"Weasley, Fred",Gryffindor
	"Weasley, George",Gryffindor
	"Weasley, Ginny",Gryffindor
	"Weasley, Percy",Gryffindor
	"Weasley, Ron",Gryffindor
	"Wood, Oliver",Gryffindor
	"Zabini, Blaise",Slytherin

Source: en.wikipedia.org/wiki/List_of_Harry_Potter_characters

Even though each “row” in the file has three values (last name, first name, and house), the first two are combined into one “column” (name), escaped with double quotes, with last name and first name separated by a comma and space. Not ideal if Hogwarts wants to send a form letter to each student, as via mail merge, since it’d be strange to start a letter with:

Dear Potter, Harry,

Rather than with, for instance:

Dear Harry,

In a file called scourgify.py, implement a program that:

  • Expects the user to provide two command-line arguments:
    • the name of an existing CSV file to read as input, whose columns are assumed to be, in order, name and house, and
    • the name of a new CSV to write as output, whose columns should be, in order, first, last, and house.
  • Converts that input to that output, splitting each name into a first name and last name. Assume that each student will have both a first name and last name. If the user does not provide exactly two command-line arguments, or if the first cannot be read, the program should exit via sys.exit with an error message.

Hints

Before You Begin

From the root of your repository execute cd 6-FileIO So your current working directory is ...

	/6-FileIO $:

Next execute

	mkdir scourgify

to make a folder called scourgify in your codespace.

Then execute

	cd scourgify

to change directories into that folder. You should now see your terminal prompt as /6-FileIO/scourgify $. You can now execute

	code scourgify.py

to make a file called scourgify.py where you’ll write your program.

How to Test

Here’s how to test your code manually:

  1. Run your program with python scourgify.py. Your program should exit using sys.exit and provide an error message:

     Too few command-line arguments

  2. Create empty files 1.csv, 2.csv, and 3.csv. Run your program with python scourgify.py 1.csv 2.csv 3.csv. Your program should output:

     Too many command-line arguments

  3. Run your program with python scourgify.py invalid_file.csv output.csv. Assuming invalid_file.csv doesn’t exist, your program should exit using sys.exit and provide an error message:

     Could not read invalid_file.csv

  4. Run your program with python scourgify.py before.csv after.csv. Assuming before.csv exists, your program should create a new file, after.csv, whose columns should be, in order, first, last, and house.

Commit your program to GITHUB

At the /6-FileIO/scourgify $ prompt in your terminal:

	git add -A

Add all changed files in the repository to be committed

	git commit -m “Upload completed scourgify.py“

Commit all changes in the REPO with the comment “Upload completed scourgify.py“ note: If the file is not complete, adjust the comment to describes what is being commited

	git push

Push all changes to the REPO