I have a model with Field like
key = CharField(max_length=100, blank=True)
when i check for the value after form submission like this.
if self.key is None:
the condition fails
But when i check for if self.key == '' it works.
My question is why it doesn't works when i evaluate it to None and works when i use ''.
The None condition works only when i assign the values like this.
key = CharField(max_length=100, null=True ,blank=True)
I read some posts where it states that when evaluating the CharField as blank=True an empty string '' is saved but they didn't shed any light why it does that. because as far i understand it should save a Null value.
null = True
is about database which means you can have an object from your model that the value of field is null.
blank= True
is about django forms and means when you fill a modelForm of this model you can pass empty string and its not necessary to fill this field in your form.
So when you add null = True for the objects that have no value for key in the database key is null and in consequence if self.key is None works but when you remove this option for the objects in the database that have no value for key in database the key is '' so your condition is not True.
Here's the code:
...
class Meta:
model = Card
def clean_video_url(self):
video_url = self.cleaned_data['video_url']
if video_url != '' and len(video_url) != YOUTUBE_VIDEO_URL_LENGTH:
pos = string.find(video_url, YOUTUBE_VIDEO_URL_IDENTIFIER)
identifier_length = len(YOUTUBE_VIDEO_URL_IDENTIFIER)
if pos == -1:
raise forms.ValidationError(_('youtube-url-not-valid'))
video_url = video_url[pos+identifier_length:pos+identifier_length+YOUTUBE_VIDEO_URL_LENGTH]
return video_url
...
def clean(self):
video_url = self.cleaned_data['video_url']
field1 = self.cleaned_data['field1']
if video_url == '' and field1 == '':
raise forms.ValidationError(_('must-fill-video-url-or-front'))
return self.cleaned_data
The most disturbing thing is that it works (submits and persists in the database) in almost all situations. It doesn't work when I write dummy text like 'aeuchah' in the video_url field, but instead it throws:
Exception Type: KeyError
Exception Value:
'video_url'
I re-read my clean_video_url method and went to see what the variables were with a debug tool like pdb.set_trace, but I can't find the problem.
UPDATE: As Marius Grigaitis and Davide R. said, the clean method is called after all the individual field methods are done. clean_video_url raised a ValidationError and returned nothing, so the clean method found nothing to work with and raised a KeyError.
You should always check that key exists in cleaned_data before using it in clean() method. You're not guaranteed that value is present in cleaned_data array if previous validations has not passed.
Documentation: https://docs.djangoproject.com/en/dev/ref/forms/validation/#cleaning-and-validating-fields-that-depend-on-each-other
By the time the form’s clean() method is called, all the individual field clean methods will have been run (the previous two sections), so self.cleaned_data will be populated with any data that has survived so far. So you also need to remember to allow for the fact that the fields you are wanting to validate might not have survived the initial individual field checks.
1.Kindly tell how can we set the limit for integer fields in django .
2.Kindly tell the codings for the block name (Add Another Choice) should be of limited for the program
class Record(models.Model):
Name = models.CharField(max_length=200,blank=True,null=True,help_text="Employee Name")
Empid = models.CharField(max_length=300,blank=True,help_text="Employee ID")
Salary = models.CharField(max_length=300,blank=True,null=True)
Bonus = models.IntegerField(blank=True,null=True)
class Choice(models.Model):
p=models.ForeignKey(Record)
Month=models.CharField(max_length=200,blank=True,null=True)
Neither can be done at the ORM level; you will need to add database-level constrains using raw SQL.
1 If you just want to check user input use a clean method
ie.
def clean_bonus(self): #thus: clean_FIELDNAME
#check the value and show an error
2 I am not sure what you mean:
a) If you mean you want users to select atleast 1 choice, but limit the maximum use something like this:
class RequireOneFormSet(BaseInlineFormSet):
"""
Require at least one form in the formset to be completed.
"""
def clean(self):
"""Check that at least one form has been completed."""
super(RequireOneFormSet, self).clean()
for error in self.errors:
if error:
return
completed = 0
for cleaned_data in self.cleaned_data:
# form has data and we aren't deleting it.
if cleaned_data and not cleaned_data.get('DELETE', False):
completed += 1
if completed < 1:
raise forms.ValidationError("At least one %s is required." %
self.model._meta.object_name.lower())
b) If you mean you want to have multiple foreign keys use django ContentTypes
I am trying to access data.get_age_display in my email template. I can't seem to get the display of this. I am not sure what I am doing wrong, I've using get_FIELD_display numerous times before but passed as context to a normal template. Is there something different with forms?
class RequestForm(forms.Form):
ADULT = 1
SENIOR = 2
STUDENT = 3
AGE_GROUP = (
(ADULT, 'Adult'),
(SENIOR, 'Senior'),
(STUDENT, 'Student'),
)
name = forms.CharField(max_length=255)
phone = forms.CharField(max_length=15)
age = forms.ChoiceField(choices=AGE_GROUP)
details = forms.CharField(widget=forms.Textarea())
def save(self):
order = Order(
name = self.cleaned_data['name'],
phone = self.cleaned_data['phone'],
age = self.cleaned_data['age'],
details = self.cleaned_data['details'],
)
order.save()
template = loader.get_template('request_email.txt')
# send over the order object in an email extracted so they can handle the ticket order
context = Context({
'data': order,
})
#import pdb; pdb.set_trace()
email_subject = 'Request Tickets'
mail_managers(email_subject, template.render(context))
in my request_email.txt all I am doing is {{ data.get_age_display }} any ideas?
Jeff
You haven't shown the code for the Order model that you're creating. Are you sure that the age field on the model has choices set?
Any reason you're not using a ModelForm? You're creating an Order object within the form's save() method, but not returning it. A modelform would do that for you, as well as removing the need to redeclare the fields for the form.
I know this is coming WAAAAAY later than the question being posted but here's my answer for completeness and anyone else who might benefit from it :-)
I'm going to assume that in AGE_GROUP, ADULT, SENIOR and STUDENT are integers. Your form cleaning will NOT automatically clean the string contained in the POST and return an integer. So in this code:
context = Context({
'data': order,
})
you would think order.age is referring to an integer but that is, in fact, incorrect. It's burned me a few times before because this will correctly save the integer to the physical table, but the order instance still has the string representation of the age field.
You could do one of two things:
1. Clean this in the field:
clean_age(self):
return int(self.cleaned_data['age'])
or create a new field type:
def MyChoiceField(forms.ChoiceField):
def clean(self, value):
if not value:
if self.required:
raise forms.ValidationError(self.error_messages['required'])
return None
else:
return None
return int(value)
link that to the form field:
age = MyChoiceField(choices=AGE_GROUP)
and then you'll be able to apply this logic to any other such choice field in future. Personally, I find the latter approach the best one and I stick all my custom field types into a form_utils file so that I can use them everywhere. Another gotcha is that forms.charField doesn't automatically strip the entered text and you can use this approach to fix that too.
I have model Foo which has field bar. The bar field should be unique, but allow nulls in it, meaning I want to allow more than one record if bar field is null, but if it is not null the values must be unique.
Here is my model:
class Foo(models.Model):
name = models.CharField(max_length=40)
bar = models.CharField(max_length=40, unique=True, blank=True, null=True, default=None)
And here is the corresponding SQL for the table:
CREATE TABLE appl_foo
(
id serial NOT NULL,
"name" character varying(40) NOT NULL,
bar character varying(40),
CONSTRAINT appl_foo_pkey PRIMARY KEY (id),
CONSTRAINT appl_foo_bar_key UNIQUE (bar)
)
When using admin interface to create more than 1 foo objects where bar is null it gives me an error: "Foo with this Bar already exists."
However when I insert into database (PostgreSQL):
insert into appl_foo ("name", bar) values ('test1', null)
insert into appl_foo ("name", bar) values ('test2', null)
This works, just fine, it allows me to insert more than 1 record with bar being null, so the database allows me to do what I want, it's just something wrong with the Django model. Any ideas?
EDIT
The portability of the solution as far as DB is not an issue, we are happy with Postgres.
I've tried setting unique to a callable, which was my function returning True/False for specific values of bar, it didn't give any errors, however seamed like it had no effect at all.
So far, I've removed the unique specifier from the bar property and handling the bar uniqueness in the application, however still looking for a more elegant solution. Any recommendations?
Django has not considered NULL to be equal to NULL for the purpose of uniqueness checks since ticket #9039 was fixed, see:
http://code.djangoproject.com/ticket/9039
The issue here is that the normalized "blank" value for a form CharField is an empty string, not None. So if you leave the field blank, you get an empty string, not NULL, stored in the DB. Empty strings are equal to empty strings for uniqueness checks, under both Django and database rules.
You can force the admin interface to store NULL for an empty string by providing your own customized model form for Foo with a clean_bar method that turns the empty string into None:
class FooForm(forms.ModelForm):
class Meta:
model = Foo
def clean_bar(self):
return self.cleaned_data['bar'] or None
class FooAdmin(admin.ModelAdmin):
form = FooForm
** edit 11/30/2015: In python 3, the module-global __metaclass__ variable is no longer supported.
Additionaly, as of Django 1.10 the SubfieldBase class was deprecated:
from the docs:
django.db.models.fields.subclassing.SubfieldBase has been deprecated and will be removed in Django 1.10.
Historically, it was used to handle fields where type conversion was needed when loading from the database,
but it was not used in .values() calls or in aggregates. It has been replaced with from_db_value().
Note that the new approach does not call the to_python() method on assignment as was the case with SubfieldBase.
Therefore, as suggested by the from_db_value() documentation and this example, this solution must be changed to:
class CharNullField(models.CharField):
"""
Subclass of the CharField that allows empty strings to be stored as NULL.
"""
description = "CharField that stores NULL but returns ''."
def from_db_value(self, value, expression, connection, contex):
"""
Gets value right out of the db and changes it if its ``None``.
"""
if value is None:
return ''
else:
return value
def to_python(self, value):
"""
Gets value right out of the db or an instance, and changes it if its ``None``.
"""
if isinstance(value, models.CharField):
# If an instance, just return the instance.
return value
if value is None:
# If db has NULL, convert it to ''.
return ''
# Otherwise, just return the value.
return value
def get_prep_value(self, value):
"""
Catches value right before sending to db.
"""
if value == '':
# If Django tries to save an empty string, send the db None (NULL).
return None
else:
# Otherwise, just pass the value.
return value
I think a better way than overriding the cleaned_data in the admin would be to subclass the charfield - this way no matter what form accesses the field, it will "just work." You can catch the '' just before it is sent to the database, and catch the NULL just after it comes out of the database, and the rest of Django won't know/care. A quick and dirty example:
from django.db import models
class CharNullField(models.CharField): # subclass the CharField
description = "CharField that stores NULL but returns ''"
__metaclass__ = models.SubfieldBase # this ensures to_python will be called
def to_python(self, value):
# this is the value right out of the db, or an instance
# if an instance, just return the instance
if isinstance(value, models.CharField):
return value
if value is None: # if the db has a NULL (None in Python)
return '' # convert it into an empty string
else:
return value # otherwise, just return the value
def get_prep_value(self, value): # catches value right before sending to db
if value == '':
# if Django tries to save an empty string, send the db None (NULL)
return None
else:
# otherwise, just pass the value
return value
For my project, I dumped this into an extras.py file that lives in the root of my site, then I can just from mysite.extras import CharNullField in my app's models.py file. The field acts just like a CharField - just remember to set blank=True, null=True when declaring the field, or otherwise Django will throw a validation error (field required) or create a db column that doesn't accept NULL.
You can add UniqueConstraint with condition of nullable_field=null and not to include this field in fields list.
If you need also constraint with nullable_field wich value is not null, you can add additional one.
Note: UniqueConstraint was added since django 2.2
class Foo(models.Model):
name = models.CharField(max_length=40)
bar = models.CharField(max_length=40, unique=True, blank=True, null=True, default=None)
class Meta:
constraints = [
# For bar == null only
models.UniqueConstraint(fields=['name'], name='unique__name__when__bar__null',
condition=Q(bar__isnull=True)),
# For bar != null only
models.UniqueConstraint(fields=['name', 'bar'], name='unique__name__when__bar__not_null')
]
Because I am new to stackoverflow I am not yet allowed to reply to answers, but I would like to point out that from a philosophical point of view, I can't agree with the most popular answer tot this question. (by Karen Tracey)
The OP requires his bar field to be unique if it has a value, and null otherwise. Then it must be that the model itself makes sure this is the case. It cannot be left to external code to check this, because that would mean it can be bypassed. (Or you can forget to check it if you write a new view in the future)
Therefore, to keep your code truly OOP, you must use an internal method of your Foo model. Modifying the save() method or the field are good options, but using a form to do this most certainly isn't.
Personally I prefer using the CharNullField suggested, for portability to models I might define in the future.
The quick fix is to do :
def save(self, *args, **kwargs):
if not self.bar:
self.bar = None
super(Foo, self).save(*args, **kwargs)
This is fixed now that https://code.djangoproject.com/ticket/4136 is resolved. In Django 1.11+ you can use models.CharField(unique=True, null=True, blank=True) without having to manually convert blank values to None.
Another possible solution
class Foo(models.Model):
value = models.CharField(max_length=255, unique=True)
class Bar(models.Model):
foo = models.OneToOneField(Foo, null=True)
I recently had the same requirement. Instead of subclassing different fields, I chose to override the save() metod on my model (named 'MyModel' below) as follows:
def save(self):
"""overriding save method so that we can save Null to database, instead of empty string (project requirement)"""
# get a list of all model fields (i.e. self._meta.fields)...
emptystringfields = [ field for field in self._meta.fields \
# ...that are of type CharField or Textfield...
if ((type(field) == django.db.models.fields.CharField) or (type(field) == django.db.models.fields.TextField)) \
# ...and that contain the empty string
and (getattr(self, field.name) == "") ]
# set each of these fields to None (which tells Django to save Null)
for field in emptystringfields:
setattr(self, field.name, None)
# call the super.save() method
super(MyModel, self).save()
If you have a model MyModel and want my_field to be Null or unique, you can override model's save method:
class MyModel(models.Model):
my_field = models.TextField(unique=True, default=None, null=True, blank=True)
def save(self, **kwargs):
self.my_field = self.my_field or None
super().save(**kwargs)
This way, the field cannot be blank will only be non-blank or null. nulls do not contradict uniqueness
For better or worse, Django considers NULL to be equivalent to NULL for purposes of uniqueness checks. There's really no way around it short of writing your own implementation of the uniqueness check which considers NULL to be unique no matter how many times it occurs in a table.
(and keep in mind that some DB solutions take the same view of NULL, so code relying on one DB's ideas about NULL may not be portable to others)