Handling Django form.save() ValueError - mysql

Question

I am a newbie to Django error handling and I spent a week trying to figure out what exactly goes wrong when trying to update a MySQL table using Django forms. I end up with ValueError: invalid literal for int() with base 10: '\x01' error. I tried to surround the erroneous code with try catch block trapping valueError and printing the row sql query, and here's what I get.
The code:
def updateTask(request, task_id):
#cur_usr_sale_point = PersonUnique.objects.filter(employees__employeeuser__auth_user = request.user.id).values_list('agreementemployees__agreement_unique__sale_point_id',flat=True)
selected_task = Tasks.objects.get(id=task_id)
responsible_people = TaskResponsiblePeople.objects.get(task_id = task_id)
task_table = Tasks. objects.all()
if request.method == 'POST':
task_form = TaskForm(request.POST,instance=selected_task)
responsible_people_form = TaskResponsiblePeopleForm(request.POST, instance = responsible_people)
if task_form.is_valid() and responsible_people_form.is_valid():
responsible_people_instance = responsible_people_form.save(commit=False)
try:
responsible_people_instance.task = task_form.save()
responsible_people_form.save()
except ValueError:
from django.db import connection
print connection.queries[-1]
return HttpResponseRedirect(reverse('task_list'))
Print gives me an absolutely valid MySQL Select-statement (to my surpise, I expected an update-statement).
The traceback without try-catch block:
Internal Server Error: /task_list/update_task/200/
Traceback (most recent call last):
File "C:\Python27\lib\site-packages\django\core\handlers\base.py", line 149, in get_response
response = self.process_exception_by_middleware(e, request)
File "C:\Python27\lib\site-packages\django\core\handlers\base.py", line 147, in get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "\\10.8.0.1\share\djprj\djprj\djprj\task\views.py", line 101, in updateTask
task_form.save();
File "C:\Python27\lib\site-packages\django\forms\models.py", line 451, in save
self.instance.save()
File "C:\Python27\lib\site-packages\django\db\models\base.py", line 700, in save
force_update=force_update, update_fields=update_fields)
File "C:\Python27\lib\site-packages\django\db\models\base.py", line 728, in save_base
updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "C:\Python27\lib\site-packages\django\db\models\base.py", line 793, in _save_table
forced_update)
File "C:\Python27\lib\site-packages\django\db\models\base.py", line 843, in _do_update
return filtered._update(values) > 0
File "C:\Python27\lib\site-packages\django\db\models\query.py", line 645, in _update
return query.get_compiler(self.db).execute_sql(CURSOR)
File "C:\Python27\lib\site-packages\django\db\models\sql\compiler.py", line 1149, in execute_sql
cursor = super(SQLUpdateCompiler, self).execute_sql(result_type)
File "C:\Python27\lib\site-packages\django\db\models\sql\compiler.py", line 837, in execute_sql
sql, params = self.as_sql()
File "C:\Python27\lib\site-packages\django\db\models\sql\compiler.py", line 1117, in as_sql
val = field.get_db_prep_save(val, connection=self.connection)
File "C:\Python27\lib\site-packages\django\db\models\fields\__init__.py", line 728, in get_db_prep_save
prepared=False)
File "C:\Python27\lib\site-packages\django\db\models\fields\__init__.py", line 720, in get_db_prep_value
value = self.get_prep_value(value)
File "C:\Python27\lib\site-packages\django\db\models\fields\__init__.py", line 1853, in get_prep_value
return int(value)
ValueError: invalid literal for int() with base 10: '\x01'
[10/Apr/2016 11:15:46] "POST /task_list/update_task/200/ HTTP/1.1" 500 126245
Help me out please !!!
EDIT: added is_valid method

Answer 1

You need to first use the form's is_valid method:
A Form instance has an is_valid() method, which runs validation routines for all its fields. When this method is called, if all fields contain valid data.
from django.shortcuts import render
from django.http import HttpResponseRedirect
from .forms import NameForm
def get_name(request):
# if this is a POST request we need to process the form data
if request.method == 'POST':
# create a form instance and populate it with data from the request:
form = NameForm(request.POST)
# check whether it's valid:
if form.is_valid():
# process the data in form.cleaned_data as required
# ...
# redirect to a new URL:
return HttpResponseRedirect('/thanks/')
# if a GET (or any other method) we'll create a blank form
else:
form = NameForm()
return render(request, 'name.html', {'form': form})
Source: Django Docs: Working with forms
I would recommend that you read the above documentation.