BooleanField that treats '0' as unchecked

def check_test(v):
    return not (
        v is False
        or v is None
        or v == ''
        or v == '0'
    )

class CheckBoxInput(forms.CheckboxInput):
    def __init__(self, attrs=None, check_test=None):
        if check_test is None:
            check_test = check_test
        return super(CheckBoxInput, self).__init__(attrs, check_test)

class BooleanField(forms.BooleanField):
    '''
    BooleanField that treats '0' as unchecked.

    '''
    widget = CheckBoxInput