Django - takes 1 positional argument but 2 were given 해결

Error

TypeError at /photo/
_add_thumb() takes 1 positional argument but 2 were given

blog/photo/fields.py의
class ThumbnailImageFieldFile(ImageFieldFile): 내부 함수

    def _add_thumb(s):

def _add_thumb(s):' » def _add_thumb(self, s):으로 변경.

에러 발생의 이유

That message has umpteen causes; the specific reason here is that all instance methods expect a first arg which by custom we call self. So declaring def method(arg): is wrong for a method, it should be def method(self, arg):. When the method dispatch tries to call method(arg): and match up two parameters self, arg against it, you get that error.

    def _add_thumb(self, s):

책의 코드가 반드시 옳은 것은 아니구나. 어디서 문제가 있었는지 확인 & 해결되었다. 참고 원글 : stackoverflow (click)