Solution for pset7 houses, CS50 2020

import.py

import sqlite3
import csv
import sys


def main():

    # checking argv (that there's one and it's a csv)
    if (len(sys.argv) != 2):
        sys.exit("Usage: import.py file.csv")

    filename = sys.argv[1]

    if not (filename.endswith(".csv")):
        sys.exit("You must provide a *.csv")

    # Connect with the .db file and make a cursor
    sqlite_file = "students.db"
    con = sqlite3.connect(sqlite_file)

    cur = con.cursor()

    # Open the csv file to import from
    with open(filename, "r") as characters:

        # Make a dictionary reader that iterates through rows
        reader = csv.DictReader(characters)

        for row in reader:
            names = []

            for part in row["name"].split(" "):
                names.append(part)

            names.append(row["house"])
            names.append(row["birth"])

            if (len(names) == 5):
                cur.execute("INSERT INTO students (first, middle, last, house, birth) VALUES(?, ?, ?, ?, ?)", names[:5])

            if (len(names) == 4):
                cur.execute("INSERT INTO students (first, last, house, birth) VALUES(?, ?, ?, ?)", names[:4])

    con.commit()
    con.close()


if __name__ == "__main__":
    main()

roster.py

import sqlite3
import csv
import sys


def main():

    # checking argv (needs to be one, house name)
    if (len(sys.argv) != 2):
        sys.exit("Usage: roster.py house_name")

    # Make house name lower to avoid cap sensitivity
    housename = sys.argv[1].lower()

    # Check if argument is indeed a house at Hogwarts
    houses = ["slytherin", "gryffindor", "ravenclaw", "hufflepuff"]

    if housename.lower() not in houses:
        sys.exit("provide house name: Gryffindor, Hufflepuff, Slytherin or Ravenclaw.")

    # Connect with the .db file and make a cursor
    sqlite_file = "students.db"
    con = sqlite3.connect(sqlite_file)

    cur = con.cursor()

    cur.execute('SELECT first, middle, last, birth FROM students WHERE lower(house) = "{}" ORDER BY last, first;'.format(housename))

    # Fetchall gives us all the rows of the table as a list of tuples with strings.
    houseroster = cur.fetchall()

    # Do stuff with each row in table
    for row in houseroster:

        if not row[1]:
            print("{} {}, born {}".format(row[0], row[2], row[3]))
        else:
            print("{} {} {}, born {}".format(row[0], row[1], row[2], row[3]))

    con.close()


if __name__ == "__main__":
    main()

No problem - I spent hours agonising over this problem, so I feel your pain!

Yes, absolutely, the input file that you will have as part of the Pset is characters.csv, so when you test the code yourself, that's the filename you'll need to use in import.py.

Then, just before you submit it via check50, change the input filename in import.py to students.csv, and it should pass check50.

Messy, but in the absence of being able to use the second command line argument as the input file (which I just couldn't get to work), it works.

Does that help?

I have submitted and I still got the same on check50. Can you please send em your code so I can see where I'm wrong?? If you don't mind, that is...

…

On Sat, 19 Dec 2020, 9:01 pm mrstoastedsnowman, ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ No problem - I spent hours agonising over this problem, so I feel your pain! Yes, absolutely, the input file that you will have as part of the Pset is characters.csv, so when you test the code yourself, that's the filename you'll need to use in import.py. Then, just before you submit it via check50, change the input filename in import.py to students.csv, and it should pass check50. Messy, but in the absence of being able to use the second command line argument as the input file (which I just couldn't get to work), it works. Does that help? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <https://gist.github.com/8491dd8f8b3e826491310f64f422f10b#gistcomment-3567316>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ARQHK2P2JXCI2QHJ5YOPV6DSVTS6NANCNFSM4LI3TJHQ> .

Not sure if we're allowed to post code, but I can tell you what I did:

with open("students.csv", "r") as data:

Then used csv.DictReader to read the data into a dictionary

Then iterated over each row in the dictionary, assigning the values from the dictionary to variables for name, house and year of birth (I used a function called split to separate the first, last and middle names into 3 separate values in a list)

Lastly, I wrote an if/else conditional that checked whether the length of the the names list was 2 or 3, and used an appropriate INSERT statement in either case to insert a new row into the table, referencing the variables listed above, but inserting None if the student has no middle name.

Pretty neat coding btw 👍