[Answer]-Custom Cleaner on Django Form – Not working

I think you might be running into issues with using other values from cleaned_data in a clean_{field} function. switch it to a general clean function and you may have better luck. Also, its better form, because its a clean method that requires two fields’ values in order for the validation to run.

def clean(self):
    cleaned_data = self.cleaned_data
    searchterm = cleaned_data.get('searchterm')
    search_type = cleaned_data.get('search_type')
    if search_type == 'regex':
        try:
            re.search(searchterm, 'randomdatastring') #this is just to test if the regex is valid
        except re.error:
            raise forms.ValidationError("Invalid regular expression.")
    return cleaned_data