CODEWITHSUNDEEP
pythondjango
Amir Afianian
Amir Afianian

Reputation: 2797

How do I retrieve a value of a field in a queryset object

I'm new to django and have the following model:

class MainFile(models.Model):
    owner = models.ForeignKey(User)
    # docfile = models.FileField(verbose_name= 'Enter you file', null=True)
    file_id = models.UUIDField(max_length=38, primary_key=True, default=1)
    file_name = models.CharField(max_length=70)
    file_suffix = models.CharField(max_length=5, blank=True, null=True)
    file_date = models.DateTimeField(auto_now_add=True, null=True)

So I want to filter a row of the table using file_id, and having that row, access the file_suffix. Currently I've found the following way but it's tricky:

obj = MainFile.objects.filter(file_id = 'e3e978a3-0375-4bb9-85a2-5175e2ec097d')
suffix = [i.file_suffix for i in obj]

I tried many ways but no luck except the above but I know that's not the correct way. How can I get the file_suffix after creating the obj using file_id as filter?

Upvotes: 3

Views: 14905

Answers (2)

misshapen
misshapen

Reputation: 328

You can do this as a one-liner with simply:

MainFile.objects.values_list('file_suffix', flat=True).get(file_id='e3e978a3-0375-4bb9-85a2-5175e2ec097d')

the values_list queryset method retrieves only the column data that you need from the database. The get method then returns the single match to your filter.

Upvotes: 7

Derek Kwok
Derek Kwok

Reputation: 13078

You can use get instead of filter

obj = MainFile.objects.get(file_id='e3e978a3-0375-4bb9-85a2-5175e2ec097d')
obj.file_suffix

Use get when your queryset will fetch at most 1 row back from the database. In this case, since file_id is marked as the primary key, you can be certain that it is unique.

Upvotes: 7

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