TIL - Django

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$ python -m venv {project-name}

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$ source project-name/bin/activate

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$ deactivate

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$ pip install django

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$ django-admin startproject mysite
$ python3 manage.py runserver

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$ python3 manage.py startapp polls

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from django.http import HttpResponse

def index(request):
    return HttpResponse("Hello, world.")

def some_url(request):
    return HttpResponse("Some ulr을 구현해 봤습니다.")

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from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path("admin/", admin.site.urls),
    path("polls/", include('polls.urls'))
]

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from django.urls import path
from . import views

urlpatterns = [
    path('',views.index, name='index')
    path('some_url',views.some_url)
]

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...
# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'polls.apps.PollsConfig', #새로 생성한 app을 settings.py에 추가
]
...

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from django.db import models

# polls app에 모델 두 개를 만들고 각각의 field를 설정

# 따로 primary key(=pk)를 설정하지 않을 경우, 모델이 생성될 때 주어지는 id와 같은 값을 갖게 됨
class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

# foreign key로 Question 모델의 pk를 참조
class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

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$ python3 manage.py makemigrations polls

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$ python3 manage.py sqlmigrate polls 0001

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$ python3 manage.py migrate

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#0001 버전으로 롤백
$ python3 manage.py migrate polls 0001

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$ python manage.py createsuperuser

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from django.contrib import admin
from .models import * # polls/models.py 에서 정의한 모델을 가져온다.

#admin site에 생성한 모델 등록
admin.site.register(Question)
admin.site.register(Choice)

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from django.db import models

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    # field 출력을 위한 함수
    def __str__(self):
        return f'제목: {self.question_text}, 날짜: {self.pub_date}'

class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

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from django.utils import timezone
import datetime

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)

    def __str__(self):
        if self.was_published_recently():
            new_badge = 'NEW!!!'
        else:
            new_badge = ''
        return f'{new_badge} 제목: {self.question_text}, 날짜: {self.pub_date}'

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$ python manage.py shell

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# 모델 가져오기
>>> from polls.models import *

#모든 Question,Choice 오브젝트 출력
>>> Question.objects.all()
>>> Choice.objects.all()

#첫번째 Choice 오브젝트를 가져와 필드 출력
>>> choice = Choice.objects.all()[0]
>>> choice.id
>>> choice.choice_text
>>> choice.votes

#첫번째 Choice와 연결된 Question을 가져와 필드 출력
>>> q = choice.question
>>> choice.question.pub_date
>>> choice.question.id

#해당 Question과 연결되어 있는 모든 Choice 가져오기
>>> q.choice_set.all()

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>>> from polls.models import *

# 새로운 Question 오브젝트를 내용과 함께 생성하고 'q1'이라는 변수에 저장
>>> q1 = Question(question_text = "커피 vs 녹차")

# 'q1' 생성시각을 설정
>>> from django.utils import timezone
>>> q1.pub_date = timezone.now()

# 'q1'을 데이터베이스에 저장하기
>>> q1.save()

# 같은 과정을 통해 q2를 생성하고 데이터베이스에 저장
>>> q2 = Question(question_text = "abc")
>>> q2.pub_date = timezone.now()
>>> q2.save()

# .create method로 Choice object를 생성하여 q2와 연결
>>> q2.choice_set.create(choice_text = "b")
# Choice object를 생성할 때 question field에 q2값을 넣어 연결
>>> choice_c = Choice(choice_text='c', question=q3)
#새로운 Choice 오브젝트를 데이터베이스에 저장하기
>>> choice_c.save()
# q2와 연결된 Choice 오브젝트들을 확인
>>> q2.choice_set.all()
<QuerySet [<Choice: b>, <Choice: c>]>

# 가장 마지막으로 생성된 오브젝트 가져와 삭제하기
>>> q = Question.objects.last()
>>> q.delete()

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# 조건에 맞는 오브젝트 필터링
>>> Question.objects.get(id=1)
>>> Question.objects.get(question_text__startswith='휴가를')
# 오브젝트 여러개를 반환하는 필터링을 진행할 경우 에러 발생
>>> Question.objects.get(pub_date__year=2023)
# get() returned more than one Question

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# 여러 오브젝트를 반환하는 필터링 가능
>>> Question.objects.filter(pub_date__year=2023)
<QuerySet [<Question: 제목: 휴가를 어디서 보내고 싶으세요?, 날짜: 2023-02-05 18:52:59+00:00>, <Question: 제목: 가장 좋아하는 디저트는?, 날짜: 2023-02-05 18:53:27+00:00>, ...]>
>>> Question.objects.filter(pub_date__year=2023).count()
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# 관계기반의 필터링
# foreign key로 지정된 Model의 필드값으로 필터링 가능
>>> Choice.objects.filter(question__question_text__startswith='휴가')
>>> Choice.objects.exclude(question__question_text__startswith='휴가')

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# example 1
>>> print(Question.objects.filter(pub_date__year=2023).query)
SELECT "polls_question"."id", "polls_question"."question_text", "polls_question"."pub_date" FROM "polls_question" WHERE "polls_question"."pub_date" BETWEEN 2023-01-01 00:00:00 AND 2023-12-31 23:59:59.999999

# example 2
# pk == primary key = id
>>> q = Question.objects.get(pk=1)
>>> print(q.choice_set.all().query)
SELECT "polls_choice"."id", "polls_choice"."question_id", "polls_choice"."choice_text", "polls_choice"."votes" FROM "polls_choice" WHERE "polls_choice"."question_id" = 1

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# startswith
>>> Question.objects.filter(question_text__startswith='휴가를')

# contains
>>> Question.objects.filter(question_text__contains='휴가')

# gt, gte, lt, lte
>>> Choice.objects.filter(votes__gt=0)

# 정규표현식
>>> print(Question.objects.filter(question_text__regex=r'^휴가.*어디').query)
SELECT "polls_question"."id", "polls_question"."question_text", "polls_question"."pub_date", "polls_question"."owner_id" FROM "polls_question" WHERE "polls_question"."question_text" REGEXP ^휴가.*어디

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from datetime import datetime, timedelta

now = datetime.now()

# one hour / one day / one week / one year later
hour_after = now + timedelta(hours=1)
day_after = now + timedelta(days=1)
week_after = now + timedelta(days=7) # weeks=1
year_after = now + timedelta(days=365)

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from django.utils import timezone

now = timezone.now()
# datetime.datetime(2023, 10, 28, 6, 25, 23, tzinfo=datetime.timezone.utc)