Pinry/pinry/pins/forms.py

from django import forms

from .models import Pin


class PinForm(forms.ModelForm):
    url = forms.CharField(label='URL')

    def clean_url(self):
        data = self.cleaned_data['url']
        image_file_types = ['png', 'gif', 'jpeg', 'jpg']
        file_type = data.split('.')[-1]
        if file_type.lower() not in image_file_types:
            raise forms.ValidationError("Requested URL is not an image file. Only images are currently supported.")
        return data

    class Meta:
        model = Pin
        exclude = ['image']