For each item update database-CodePudding

I'm a total beginner with Python/Django and trying to understand why this isn't working. I have a function that contains a for loop, doing some logic and then updating a model. but when I have more than 1 item in the loop I get a UNIQUE constraint failed: app_token.token_name error.

So I think I'm misunderstanding how the loop is working?

function

    tokens = Token.objects.all()
    for item in tokens:
        if item.token_contract_address is not None:          
            token = Token.objects.get(pk=item.id)
            parameters = {
                'address':token.token_contract_address
            } 
            session = Session()
            session.headers.update(headers)
            response = session.get(url, params=parameters)
            resp = json.loads(response.text)
            token_id = (resp['data'][next(iter(resp['data']))]['id'])
            logo = (resp['data'][next(iter(resp['data']))]['logo'])

            url = 'https://pro-api.coinmarketcap.com/v1/cryptocurrency/quotes/latest'
            parameters = {
                'id':token_id
            }
            session = Session()
            session.headers.update(headers)
            response = session.get(url, params=parameters) 
            id = str(token_id)
            price = (json.loads(response.text)['data'][id]['quote']['USD']['price'])
            market_cap = (json.loads(response.text)['data'][id]['quote']['USD']['market_cap'])
            change = (json.loads(response.text)['data'][id]['quote']['USD']['percent_change_24h'])

            r = Token.objects.update(token_capture_date = formatedDate, token_price = price, token_name=item.token_name )

I'm expecting the this Token.objects.update(token_capture_date = formatedDate, token_price = price, token_name=item.token_name ) to update the model based on the item loop?

The model is very simple:

class Token(models.Model):

    token_name = models.CharField(max_length=50, blank=False, unique=True)
    token_slug = models.CharField(max_length=50, blank=True,null=True)
    token_price = models.FloatField(blank=True,null=True)
    token_capture_date = models.DateField(blank=True,null=True)
    token_contract_address = models.CharField(max_length=50, blank=True,null=True)

    def __str__(self):
        return str(self.token_name)

I'm using the update on the objects and have tried removing the token_name, and tried using token.token_name

If I remove token_name= it updates both items in the database with the same values? which makes me think its this line r = Token.objects.update(token_capture_date = formatedDate, token_price = price, token_name=item.token_name ) do i need to apply some kinda of filter?

Thanks

CodePudding user response：

I believe that by calling Token.objects.update() you actually end up trying to update all Token objects. Since token_name has to be unique, and you are giving it the same name as another Token object it throws that error. Since you are already in a for loop, you can simply update the token that is currently being processed.

My suggestion would be to use this code instead:

item.token_capture_date = formattedDate
item.token_price = price
item.save()

This will make it so that the current token object which is being processed in the for loop has its respective field values updated and saved in the database.

Also, this line is unnecessary: token = Token.objects.get(pk=item.id) as we already have access to the token through the looping variable item.

Do let me know if this helps!