CODEWITHSUNDEEP
pythondjango
tangjikededela
tangjikededela

Reputation: 41

How to delete special data from database by python django

For example, I have a table called BlackList in the database which looks like this:

enter image description here

and the model of the table is:

class BlackList(models.Model):
    list = models.CharField(max_length=1000, null=True, blank=True)

What I try to do is:

if request.method == "POST":
    username = request.POST.get('username')  # Get username input first
    password = request.POST.get('password')
    user = authenticate(request, username=username, password=password)
    BL = BlackList.objects.values_list('list', flat=True) # Read all data into array
    if username in BL:  # Check if the username is in blacklist
       # Remove this username from the BlackList table

So my question is how to delete the special data for a special, for example, if 'aaa' try to log in, then 'aaa' will be removed or deleted from the BlackList table.

Upvotes: 1

Views: 118

Answers (2)

Preeti Y.
Preeti Y.

Reputation: 535

You can use filter() in combination with first() to get the exist username:

blacklist = Blacklist.objects.filter(username=username).first()

(This will return None if there is no match. If you use get(), you will get DoesNotExist error instead -- which is not preferred.)

After that, you can just delete it:

blacklist.delete()

It will take 2 queries (get and delete) to achieve your goal.

An alternative way is to delete it without getting the object:

Blacklist.objects.filter(username=username).delete()

This statement will be execute with only one query which is equals DELETE FROM ... WHERE username='username'

Upvotes: 2

I_Can_Help
I_Can_Help

Reputation: 579

There is .delete method. I. e. try this:

if BlackList.filter(list=username).exists(): 
    BlackList.objects.get(list=username).delete()

instead of:

BL = BlackList.objects.values_list('list', flat=True) # Read all data into array 
if username in BL: # Check if the username is in blacklist 
    # Remove this username from the BlackList table

You can read more about that on https://docs.djangoproject.com/en/3.0/topics/db/queries/#deleting-objects and https://docs.djangoproject.com/en/3.0/ref/models/querysets/#exists

Upvotes: 2

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