django queryset api - using values method with a list of fields

Question

I would like to make a query to a Django Model, but I do not know the fields to retrieve in advance. If I happen to know them and their number, I would do

MyModel.objects.values('field1', 'field2')

Indeed, I noticed that the values method takes optional positional arguments, *fields, as specified in the API reference.

Therefore, I thought of making a function, which takes *fields arguments and then using such args for my query. The wrapper would look like this:

def get_values(self, *fields):
   return MyModel.objects.values(fields)

However, I get an AttributeError: 'tuple' object has no attribute 'split' as the QuerySet API does not like my tuple. How could I work it out?

pawamoy · Accepted Answer · 2018-03-28 14:32:09Z

2

You need to unpack the values :)

def get_values(self, *fields):
    return MyModel.objects.values(*fields)  # note the *

Otherwise it would be like you wrote

def get_values(self, *fields):
    return MyModel.objects.values(('field1', 'field2'))  # note the extra ()

... hence the AttributeError: 'tuple' object has no attribute 'split' because tuples do not have the split method!

answered Mar 28, 2018 at 14:32

pawamoy

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Luan Fonseca · Accepted Answer · 2018-03-28 14:33:35Z

2

You can use the python unpacking feature: The * operator can be used to send a list of params as positional arguments:

>>> fields = ['field1', 'fields2']
>>> MyModel.objects.values(*fields)
<MyModelQueryset [{'field1': 'foo1', 'field2': 'bar2'}, {'field1': 'foo1', 'field2': 'bar2'}, {'field1': 'foo1', 'field2': 'bar2'}]>

answered Mar 28, 2018 at 14:33

Luan Fonseca

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