How Django Helps You Land a Data Engineer Job Faster

# sales/management/commands/load_daily_sales.py
import csv
from decimal import Decimal
from django.core.management.base import BaseCommand
from django.db import transaction
from sales.models import DailySale

class Command(BaseCommand):
    help = "Load daily sales from a CSV file"

    def add_arguments(self, parser):
        parser.add_argument("path")

    @transaction.atomic
    def handle(self, *args, **opts):
        count = 0
        with open(opts["path"], newline="", encoding="utf-8") as f:
            for row in csv.DictReader(f):
                DailySale.objects.update_or_create(
                    day=row["day"], store=row["store"],
                    defaults={"amount": Decimal(row["amount"])},
                )
                count += 1
        self.stdout.write(self.style.SUCCESS(f"Loaded {count} rows"))

python manage.py load_daily_sales data/sales_2026-11-05.csv

# crontab: run every day at 02:30
30 2 * * * cd /opt/salesapp && /opt/venv/bin/python manage.py load_daily_sales /data/sales_latest.csv >> load.log 2>&1

# sales/models.py
from django.db import models

class DailySale(models.Model):
    day = models.DateField()
    store = models.CharField(max_length=50)
    amount = models.DecimalField(max_digits=12, decimal_places=2)
    quality_flag = models.CharField(max_length=30, blank=True)   # e.g. "negative_amount"
    reviewed = models.BooleanField(default=False)

    class Meta:
        constraints = [models.UniqueConstraint(fields=["day", "store"], name="uniq_day_store")]

# sales/admin.py
from django.contrib import admin
from .models import DailySale

@admin.action(description="Mark selected rows as reviewed")
def mark_reviewed(modeladmin, request, queryset):
    queryset.update(reviewed=True)

@admin.register(DailySale)
class DailySaleAdmin(admin.ModelAdmin):
    list_display = ("day", "store", "amount", "quality_flag", "reviewed")
    list_filter = ("quality_flag", "reviewed", "store")
    search_fields = ("store",)
    readonly_fields = ("amount",)
    actions = [mark_reviewed]

# sales/api.py
from rest_framework import serializers, viewsets
from .models import DailySale

class DailySaleSerializer(serializers.ModelSerializer):
    class Meta:
        model = DailySale
        fields = ["day", "store", "amount"]

class DailySaleViewSet(viewsets.ReadOnlyModelViewSet):
    serializer_class = DailySaleSerializer

    def get_queryset(self):
        qs = DailySale.objects.filter(reviewed=True).order_by("-day")
        store = self.request.query_params.get("store")
        return qs.filter(store=store) if store else qs

# settings.py
REST_FRAMEWORK = {
    "DEFAULT_PAGINATION_CLASS": "rest_framework.pagination.PageNumberPagination",
    "PAGE_SIZE": 500,
}
# GET /api/daily-sales/?store=noida-01&page=2

sales-data/
├── manage.py
├── config/
├── sales/
│   ├── models.py
│   ├── admin.py
│   ├── api.py
│   └── management/commands/
│       ├── load_daily_sales.py
│       └── flag_quality_issues.py
└── README.md

# sales/management/commands/flag_quality_issues.py
from django.core.management.base import BaseCommand
from sales.models import DailySale

class Command(BaseCommand):
    help = "Flag rows that break simple quality rules"

    def handle(self, *args, **opts):
        n = DailySale.objects.filter(amount__lt=0, quality_flag="").update(
            quality_flag="negative_amount")
        self.stdout.write(f"Flagged {n} rows")

# Sales data service (Django)
- load_daily_sales: idempotent CSV load (update_or_create)
- flag_quality_issues: rule-based quality flags
- Admin: review and mark flagged rows
- API: /api/daily-sales/ (reviewed rows, paginated)
Limits: suitable for small daily volumes; larger loads use warehouse SQL