DJANGO CookBook - File type validation in form

forms.py

# Tested in Django 1.6

class ImportForm(forms.Form):
    csv_file = forms.FileField(label=_('Select CSV file'))

    def clean_csv_file(self):
        f = self.cleaned_data['csv_file']

        if not f.content_type in ['text/csv',]:
            raise forms.ValidationError(_("The file type is not accepted."))

        return f