Django: How to increment a counter stored in models.py / Database - django

Question

I have created a small counter model class Counter to store the amount of times a small survey application has been completed.
I want to increment SurveyWizardOneCounter in my models.py from my def done() method in my views.py
Can anyone tell me how to do this?
Previously I was using Global variables for my counter which I have found out do not work properly with a web app. I am trying to learn how to create and store a counter in my DB. Any help is appreciated.
models.py
class Counter(models.Model):
SurveyWizardOneCounter = models.SmallIntegerField()
TotalMaxCounter = models.SmallIntegerField()
views.py
from survey.models import Counter
def done(self, form_list, **kwargs):
Counter.SurveyWizardOneCounter += 1 # This is where I am trying to increment the counter
logger.debug('\n\n SurveyWizardOneCounter = %s', SurveyWizardOneCounter)
for form in form_list:
form.save()
return render(self.request, 'Return_to_AMT.html', {
'form_data': [form.cleaned_data for form in form_list],
})

Answer 1

Since you have 9 different survey counters and you need to increment each counter when a survey is submitted, it would be better if you define a field survey_wizard_type with its possible values being survey_wizard_one, survey_wizard_two till survey_wizard_nine and a field survey_wizard_count having default value 0 which stores the count for that particular survey wizard. There would be 9 records in your database for Counter model then.
models.py
SURVEY_WIZARD_TYPE_CHOICES = ['survey_wizard_one', 'survey_wizard_two', 'survey_wizard_three', 'survey_wizard_four', 'survey_wizard_five', 'survey_wizard_six', 'survey_wizard_seven', 'survey_wizard_eight', 'survey_wizard_nine']
class Counter(models.Model):
survey_wizard_type = models.CharField(choices=SURVEY_WIZARD_TYPE_CHOICES)
survey_wizard_count = models.SmallIntegerField(default=0)
total_max_counter = models.SmallIntegerField()
Then in your views.py, you can use get_or_create method for looking up an Counter object with the given survey_wizard_type, creating one if necessary. Then increment the survey_wizard_count by 1 and save that object into the database.
views.py
from django.db.models import F
from survey.models import Counter
def done(self, form_list, **kwargs):
survey_counter = Counter.objects.get_or_create(survey_wizard_type= 'survey_wizard_x') # x can be any value from one to nine
survey_counter.survey_wizard_count = F('survey_wizard_count') + 1
survey_counter.save()
logger.debug('\n\n SurveyWizardOneCounter = %s', SurveyWizardOneCounter)
for form in form_list:
form.save()
return render(self.request, 'Return_to_AMT.html', {
'form_data': [form.cleaned_data for form in form_list],
})
EDIT
Rahul provided the solution but this is the code I ended up using
models.py
class Counter(models.Model):
SURVEY_WIZARD_TYPE_CHOICES = (
('SURVEY_WIZARD_ONE', 'survey_wizard_one'),
('SURVEY_WIZARD_TWO', 'survey_wizard_two'),
('SURVEY_WIZARD_THREE', 'survey_wizard_three'),
('SURVEY_WIZARD_FOUR', 'survey_wizard_four'),
('SURVEY_WIZARD_FIVE', 'survey_wizard_five'),
('SURVEY_WIZARD_SIX', 'survey_wizard_six'),
('SURVEY_WIZARD_SEVEN', 'survey_wizard_seven'),
('SURVEY_WIZARD_EIGHT', 'survey_wizard_eight'),
('SURVEY_WIZARD_NINE', 'survey_wizard_nine'),
)
survey_wizard_type = models.CharField(max_length=1000, choices=SURVEY_WIZARD_TYPE_CHOICES)
survey_wizard_count = models.SmallIntegerField(default=0)
total_max_counter = models.SmallIntegerField(default=0)
views.py
def done(self, form_list, **kwargs):
survey_counter = Counter.objects.get_or_create(survey_wizard_type= 'survey_wizard_one')[0] # x can be any value from one to nine
survey_counter.survey_wizard_count = F('survey_wizard_count') + 1
survey_counter.save()
for form in form_list:
form.save()
return render(self.request, 'Return_to_AMT.html', {
'form_data': [form.cleaned_data for form in form_list],
})

Answer 2

I will assume your Counter model will store just one record.
c = Counter.objects.get()
c.SurveyWizardOneCounter += 1
# Update another attributes if you need
c.save()
Or maybe
from django.db.models import F
Counter.objects.filter().update(SurveyWizardOneCounter=F('SurveyWizardOneCounter')+1)

Answer 3

You should make sure you use an atomic method to update the field, some of the answers above could have a race condition between update and save. The Django documentation suggests to use the following method:
from django.db.models import F
product = Product.objects.get(name='Venezuelan Beaver Cheese')
product.number_sold = F('number_sold') + 1
product.save()