invalid literal for int() with base 10: 'string'

Question

I'm trying lookup the database that match specific campus_id. This works if I use integers, but doesn't work with strings.

models.py

from django.db import models

class Campus(models.Model):
   campus_id = models.IntegerField(primary_key=True)
   name = models.CharField(max_length=100)

   def __str__(self):
      return self.name

class Restaurant(models.Model):
   restaurant_id = models.IntegerField(primary_key=True)
   name = models.CharField(max_length=100)
   location = models.CharField(max_length=100)
   campus_id = models.ForeignKey(Campus,on_delete = models.CASCADE)
   opening_hours = models.TimeField()
   closing_hours = models.TimeField()
   capacity = models.IntegerField()
   #staff = models.IntegerField()

   def __str__(self):
      return self.name

views.py

def restaurants(request):
    query = request.GET.get('search', None)
    context = {}
    if query and request.method == 'GET':
        results = Restaurant.objects.filter(campus_id=query)
        context.update({'results':results})
        return render(request, 'eatatdcu/restaurants.html', context)

restaurants.html

{% for x in results %}


        {{x.name}} , {{x.location}}

        <br>

    {% endfor %}

Traceback log

Traceback (most recent call last):
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\exception.py", line 41, in inner
        response = get_response(request)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\base.py", line 187, in _get_response
        response = self.process_exception_by_middleware(e, request)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\core\handlers\base.py", line 185, in _get_response
        response = wrapped_callback(request, *callback_args, **callback_kwargs)
      File "C:\Users\Calvin\Desktop\CA377\2019-ca377-EatAtDCU\src\ca377\eatatdcu\views.py", line 13, in restaurants
        results = Restaurant.objects.filter(campus_id=query)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\manager.py", line 85, in manager_method
        return getattr(self.get_queryset(), name)(*args, **kwargs)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\query.py", line 781, in filter
        return self._filter_or_exclude(False, *args, **kwargs)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\query.py", line 799, in _filter_or_exclude
        clone.query.add_q(Q(*args, **kwargs))
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\sql\query.py", line 1260, in add_q
        clause, _ = self._add_q(q_object, self.used_aliases)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\sql\query.py", line 1286, in _add_q
        allow_joins=allow_joins, split_subq=split_subq,
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\sql\query.py", line 1216, in build_filter
        condition = lookup_class(lhs, value)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\lookups.py", line 24, in __init__
        self.rhs = self.get_prep_lookup()
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\fields\related_lookups.py", line 110, in get_prep_lookup
        self.rhs = target_field.get_prep_value(self.rhs)
      File "C:\Users\Calvin\AppData\Local\Programs\Python\Python36\lib\site-packages\django\db\models\fields\__init__.py", line 1849, in get_prep_value
        return int(value)
    ValueError: invalid literal for int() with base 10: 'dcu alpha'

Answer 1

I see in the error message that you tried to search for the value dcu alpha in the field Restaurant.campus_id (which is a ForeignKey, so in the database it will have the type of the PK of the model Campus, which is an integer). Django tries to cast the search value to an int because the field is an integer.

Maybe you want to search a different field, maybe:

• name (the name of the Restaurant instances)
• or campus_id__name (the name of the Campus instance belonging to the Restaurant instances)?

Or you could add error handling:

def restaurants(request):
    query = request.GET.get('search', None)
    context = {}
    if query and request.method == 'GET':
        try:
            query_int = int(query)
        except ValueError:
            query_int = -1

        results = Restaurant.objects.filter(campus_id=query_int)
        context.update({'results':results})
        return render(request, 'eatatdcu/restaurants.html', context)