First Django Admin

Act 3: Hello loader

Our next challenge is to load the source CSV file into the model.

We are going to do this using Django’s system for management commands. It allows us to make our own manage.py commands like migrate and startapp that take advantage of Django’s bag of tricks and interact with the database.

To do this, add a management/commands directory in our academy app, complete with empty __init__.py files required by Python. You can do this in your operating system’s file explorer, or on the command line. From a Linux or OSX prompt that would look something like this.

# The -p flag here makes both new directories
mkdir -p academy/management/commands
# This creates the empty files on Macs or in Linux
touch academy/management/__init__.py
touch academy/management/commands/__init__.py

From Windows something more like this:

# If you're in Windows create them with your text editor
start notepad++ academy/management/__init__.py
start notepad++ academy/management/commands/__init__.py

When you’re done the app’s directory should look something like this.

academy/
    __init__.py
    admin.py
    apps.py
    models.py
    management/
        __init__.py
        commands/
            __init__.py
    migrations/
    tests.py
    views.py

Create a new file in the management/commands directory where the new command will go. Let’s call it loadacademycsv.py.

# Mac or Linux
touch academy/management/commands/loadacademycsv.py
# Windows
start notepad++ academy/management/commands/loadacademycsv.py

Open it up and paste in the skeleton common to all management commands.

from django.core.management.base import BaseCommand

class Command(BaseCommand):

    def handle(self, *args, **options):
        print("Loading CSV")

Running it is as simple as invoking its name with manage.py.

python manage.py loadacademycsv

Download the source CSV file from GitHub and store it in your base directory next to manage.py.

Return to the management command and introduce Python’s built-in csv module, which can read and files CSV files.

import csv
from django.core.management.base import BaseCommand

class Command(BaseCommand):

    def handle(self, *args, **options):
        print "Loading CSV"

Next add a variable beneath the print command that contains the path to where you’ve saved the CSV file. If you’ve saved it next to manage.py, that is as simple as starting off with “./”.

import csv
from django.core.management.base import BaseCommand

class Command(BaseCommand):

    def handle(self, *args, **options):
        print "Loading CSV"
        csv_path = "./academy_invites_2014.csv"

:::{note} In case you don’t already know, a “variable” is a fancy computer programming word for a named shortcut where we save our work as we go. :::

Now access the file at that path with Python’s built-in open function.

import csv
from django.core.management.base import BaseCommand

class Command(BaseCommand):

    def handle(self, *args, **options):
        print "Loading CSV"
        csv_path = "./academy_invites_2014.csv"
        csv_file = open(csv_path, 'rb')

Feeding the file object it creates into the csv module’s DictReader will return a list with each row read to work with.

import csv
from django.core.management.base import BaseCommand

class Command(BaseCommand):

    def handle(self, *args, **options):
        print "Loading CSV"
        csv_path = "./academy_invites_2014.csv"
        csv_file = open(csv_path, 'rb')
        csv_reader = csv.DictReader(csv_file)

Create a loop that walks through the list, printing out each row as it goes by.

import csv
from django.core.management.base import BaseCommand

class Command(BaseCommand):

    def handle(self, *args, **options):
        print "Loading CSV"
        csv_path = "./academy_invites_2014.csv"
        csv_file = open(csv_path, 'rb')
        csv_reader = csv.DictReader(csv_file)
        for row in csv_reader:
            print row

Run it to see what we mean.

python manage.py loadacademycsv

Import our model into the command and use it to save the CSV records to the database.

import csv
from academy.models import Invite
from django.core.management.base import BaseCommand

class Command(BaseCommand):

    def handle(self, *args, **options):
        print "Loading CSV"
        csv_path = "./academy_invites_2014.csv"
        csv_file = open(csv_path, 'rb')
        csv_reader = csv.DictReader(csv_file)
        for row in csv_reader:
            obj = Invite.objects.create(
                name=row['Name'],
                branch=row['Branch']
            )
            print obj

Run it again and you’ve done it. The CSV is loaded into the database.

python manage.py loadacademycsv