How do you use the django 1.2 form validators?

Question

I have been trying to use the new validators that are now included with Django. I have set the validators parameter on my fields and while I don't get an error, the validation doesn't seem to be working. Here is my console session that dupplicates the issue.

Python 2.7 (r27:82525, Jul  4 2010, 09:01:59) [MSC v.1500 32 bit (Intel)] on win32 
Type "help", "copyright", "credits" or "license" for more information. 
(InteractiveConsole)
>>> import django
>>> django.VERSION
(1, 2, 1, 'final', 0)
>>> from django.core import validators
>>> from django import forms
>>> field = forms.CharField(validators=[validators.MinValueValidator(2)])
>>> field.clean("s") 
u's'

I would expect the field.clean("s") to throw a validation exception since there is only one character in the string. I realize it is possible that I am misunderstanding how to use the validators, so any help would be greatly appreciated.

Answer 1

I think you want to try the MinLengthValidator instead of the MinValueValidator.

The MinValueValidator checks that the field value is greater or equal to the given value.

>>> 's' > 2
True

Since "s" > 2, no validation error is raised.

It would make more sense to use the MinValueError with an IntegerField or FloatField.

>>> field = forms.FloatField(validators=[validators.MinValueValidator(2)])
>>> field.clean(5)
5.0
>>> field.clean(1.9)
...
ValidationError: [u'Ensure this value is greater than or equal to 2.']

To ensure that a string has a certain length, use the MinLengthValidator.

>>> field = forms.CharField(validators=[validators.MinLengthValidator(2)])
>>> field.clean('abc')
u'abc'
>>> field.clean('s')
...
ValidationError: [u'Ensure this value has at least 2 characters (it has 1).']