(Django) Trim whitespaces from charField

Question

How do I strip whitespaces (trim) from the end of a charField in Django?

Here is my Model, as you can see I've tried putting in clean methods but these never get run.

I've also tried doing name.strip(), models.charField().strip() but these do not work either.

Is there a way to force the charField to trim automatically for me?

Thanks.

from django.db import models
from django.forms import ModelForm
from django.core.exceptions import ValidationError
import datetime

class Employee(models.Model):
    """(Workers, Staff, etc)"""
    name                = models.CharField(blank=True, null=True, max_length=100)

    def save(self, *args, **kwargs):
        try:
            # This line doesn't do anything??
            #self.full_clean()
            Employee.clean(self)
        except ValidationError, e:
            print e.message_dict

        super(Employee, self).save(*args, **kwargs) # Real save

    # If I uncomment this, I get an TypeError: unsubscriptable object
    #def clean(self):
    #   return self.clean['name'].strip()

    def __unicode__(self):
        return self.name

    class Meta:
        verbose_name_plural = 'Employees'

    class Admin:pass


class EmployeeForm(ModelForm):
    class Meta:
        model = Employee

    # I have no idea if this method is being called or not  
    def full_clean(self):       
        return super(Employee), self.clean().strip()
        #return self.clean['name'].strip()

Edited: Updated code to my latest version. I am not sure what I am doing wrong as it's still not stripping the whitespace (trimming) the name field.

Answer 1

When you're using a ModelForm instance to create/edit a model, the model's clean() method is guaranteed to be called. So, if you want to strip whitespace from a field, you just add a clean() method to your model (no need to edit the ModelForm class):

class Employee(models.Model):
    """(Workers, Staff, etc)"""
    name = models.CharField(blank=True, null=True, max_length=100)

    def clean(self):
        if self.name:
            self.name = self.name.strip()

I find the following code snippet useful- it trims the whitespace for all of the model's fields which subclass either CharField or TextField (so this also catches URLField fields) without needing to specify the fields individually:

def clean(self):
    for field in self._meta.fields:
        if isinstance(field, (models.CharField, models.TextField)):
            value = getattr(self, field.name)
            if value:
                setattr(self, field.name, value.strip())

Someone correctly pointed out that you should not be using null=True in the name declaration. Best practice is to avoid null=True for string fields, in which case the above simplifies to:

def clean(self):
    for field in self._meta.fields:
        if isinstance(field, (models.CharField, models.TextField)):
            setattr(self, field.name, getattr(self, field.name).strip())

Answer 2

Model cleaning has to be called (it's not automatic) so place some self.full_clean() in your save method.
http://docs.djangoproject.com/en/dev/ref/models/instances/#django.db.models.Model.full_clean

As for your form, you need to return the stripped cleaned data.

return self.cleaned_data['name'].strip()

Somehow I think you just tried to do a bunch of stuff that doesn't work. Remember that forms and models are 2 very different things.

Check up on the forms docs on how to validate forms http://docs.djangoproject.com/en/dev/ref/forms/validation/

super(Employee), self.clean().strip() makes no sense at all!

Here's your code fixed:

class Employee(models.Model):
    """(Workers, Staff, etc)"""
    name = models.CharField(blank=True, null=True, max_length=100)

    def save(self, *args, **kwargs):
        self.full_clean() # performs regular validation then clean()
        super(Employee, self).save(*args, **kwargs)


    def clean(self):
        """
        Custom validation (read docs)
        PS: why do you have null=True on charfield? 
        we could avoid the check for name
        """
        if self.name: 
            self.name = self.name.strip()


class EmployeeForm(ModelForm):
    class Meta:
        model = Employee


    def clean_name(self):
        """
        If somebody enters into this form ' hello ', 
        the extra whitespace will be stripped.
        """
        return self.cleaned_data.get('name', '').strip()

Answer 3

I'm handling this in views as a decorator. I'm also truncating field values that exceed a CharField max_length value.

from django import forms
from django import models
from django.db.models.fields import FieldDoesNotExist
from django.utils.encoding import smart_str

class CleanCharField(forms.CharField):
        """Django's default form handling drives me nuts wrt trailing
        spaces.  http://code.djangoproject.com/attachment/ticket/6362
        """
        def clean(self, value):
            if value is None:
                value = u''
            value = smart_str(value).strip()
            value = super(forms.CharField, self).clean(value)
            return value

def truncate_charfield(model):
    """decorator to truncate CharField data to model field max_length.
    Apply to the clean method in views Form:

    @truncate_charfield(MyModel)
    def clean(self):
        ...
    """
    def wrap(f):
        def wrapped_f(*args):
            f(*args)
            d = args[0].cleaned_data
            for field in model._meta.fields:
                try:
                    mf = model._meta.get_field(field.name)
                    if isinstance(mf, models.CharField) and field.name in d:
                        d[field.name] = d[field.name][:mf.max_length]
                except FieldDoesNotExist:
                    pass
            return d
        return wrapped_f
    return wrap

Answer 4

If you have so many data-fields to be trimmed, why not try extending CharField?

from django.db import models
from django.utils.translation import ugettext_lazy as _

class TrimCharField(models.CharField):
   description = _(
       "CharField that ignores leading" 
       " and trailing spaces in data")

   def get_prep_value(self, value)
       return trim(super(TrimCharField, self
           ).get_prep_value(value))

   def pre_save(self, model_instance, add):
       return trim(super(TrimCharField, self
           ).pre_save(model_instance, add))

UPDATE: For Django versions <= 1.7 if you want to extend field, you are to use models.SubfieldBase metaclass. So here it will be like:

class TrimCharField(six.with_metaclass(
    models.SubfieldBase, models.CharField)):

Answer 5

Django 1.9 offers a simple way of accomplishing this. By using the strip argument whose default is True, you can make sure that leading and trailing whitespace is trimmed. You can only do that in form fields though in order to make sure that user input is trimmed. But that still won't protect the model itself. If you still want to do that, you can use any of the methods above.

For more information, visit https://docs.djangoproject.com/en/1.9/ref/forms/fields/#charfield

Answer 6

If you're still not on Django 1.9+ shame on you (and me) and drop this into your form. This is similar to @jeremy-lewis's answer but I had several problems with his.

def clean_text_fields(self):
    # TODO: Django 1.9, use on the model strip=True
    # https://docs.djangoproject.com/en/1.9/ref/forms/fields/#charfield
    from django.forms.fields import CharField
    cd = self.cleaned_data
    for field_name, field in self.fields.items():
        if isinstance(field, CharField):
            cd[field_name] = cd[field_name].strip()
            if self.fields[field_name].required and not cd[field_name]:
                self.add_error(field_name, "This is a required field.")

def clean(self):
    self.clean_text_fields()