django 自定义校验

#A validator is a callable that takes a value and raises a
#ValidationError if it doesn’t meet some criteria. Validators can be useful
#for re-using validation logic between different types of fields.
#For example, here’s a validator that only allows even numbers:

from django.core.exceptions import ValidationError
    def validate_even(value):
        if value % 2 != 0:
            raise ValidationError(u’%s is not an even number’ % value)

#You can add this to a model field via the field’s validators argument:

from django.db import models
class MyModel(models.Model):
    even_field = models.IntegerField(validators=[validate_even])

#Because values are converted to Python before validators are run, you can
#even use the same validator with forms:

from django import forms
class MyForm(forms.Form):
    even_field = forms.IntegerField(validators=[validate_even])