Kim Majali

Add Field to QuerySet to Store Computation Results

Kim Majali wrote on 06/06/2022

Way 1: Annotate() & Query Expressions

How many chairs are needed for each company to seat all employees?

from django.db.models import F

company = Company.objects.filter(
   num_employees__gt=F('num_chairs')).annotate(
   chairs_needed=F('num_employees') - F('num_chairs')).first()

Django Redirect/Reverse/Render in View

Kim Majali wrote on 03/06/2022

1. Redirect (will prevent resubmitting the form, no context to update)

from django.shortcuts import redirect
return redirect('glossaries')

Django Loop to Update Multiple Objects

Kim Majali wrote on 03/06/2022

Set filed name this way name="sub_service_{{ service.id }}"

In View data will be the name fo the field in the loop, request.POST[data] is the value

for data in request.POST:
        if "sub_service_" in data:
            sub_service_id = int(data.replace("sub_service_", ""))
            CompanySubService.objects.select_for_update().filter(id=sub_service_id).update(delivery_per_hour = request.POST[data])

Example with try and message

if request.POST.get("form_type") == 'update_sub_services_delivery':
    try:
        for data in request.POST:
            if "sub_service_" in data:
                sub_service_id = int(data.replace("sub_service_", ""))
                CompanySubService.objects.select_for_update().filter(id=sub_service_id).update(delivery_per_hour = request.POST[data])
        messages.success(request, "Sub services delivery info has been updated." )
    except Exception as e:
        print("Exception update_sub_services_delivery ==========================")
        messages.error(request, "Error. Something went wrong.")
        print(e)
        print("End of Exception  ==========================")
        
    return render(request, template_name, context)

Django Checkbox, Text and Select

Kim Majali wrote on 03/06/2022

Checkbox

record.full_timer = request.POST.get('full_timer', False)
if record.full_timer == 'on':
    record.full_timer = True
    
record.save(update_fields=['full_timer'])
print('record updated')

Django URLs

Kim Majali wrote on 03/06/2022

Basic urls

from django.conf.urls import url
from boards import views

urlpatterns = [
    url(r'^$', views.home, name='home'),
    url(r'^about/$', views.about, name='about'),
]

Deeper URL structures:

urlpatterns = [
    url(r'^$', views.home, name='home'),
    url(r'^about/$', views.about, name='about'),
    url(r'^about/company/$', views.about_company, name='about_company'),
]

Advanced urls (with regex) eg: this will create a url of each username

from django.conf.urls import url
from boards import views

urlpatterns = [
    url(r'^$', views.home, name='home'),
    url(r'^(?P[\w.@+-]+)/$', views.user_profile, name='user_profile'),
]

Parameters

1. Parameters as part of url: eg: /users/5

url(r'^users/(?P\d+)/$', 'viewname', name='urlname')

Function-based view

def viewname(request, user_id):
    user = User.objects.get(id=user_id)

Class-based view

class SampleView(TemplateView):
    def get_context_data(self, **kwargs):
        user = User.objects.get(id=kwargs['user_id'])

2. GET parameters eg: /products?price_lte=5000

url(r'^products/$', 'viewname', name='urlname')

def viewname(request):
    price_lte = request.GET['price_lte']

3. POST parameters

url(r'^register/$', 'register', name='urlname')

def register(request):
    form = RegisterForm()
    if request.method == "POST":
        form = RegisterForm(request.POST) #if no files
        if form.is_valid():
            #do something if form is valid
    context = {
        'form': form
    }
    return render(request, "template.html", context)

Match string after drinks/ prefix

path('drinks//',...),

Match one or more characters (non-digit regular expression) after drinks/ prefix

re_path(r'^drinks/(?P\D+)/',...),

Match integer after stores/ prefix

path('stores//',...),

Match one or more digits (digit regular expression) after stores/ prefix

re_path(r'^stores/(?P\d+)/',...),