keywords_in_abstract = []

for ab in downloaded_abstracts:

        keyword_box = []

        words = ab.replace('.','').split(' ')

        for w in words: 
                if w.upper() = disease:    
                        keyword_box.append(w.upper())

        for w in words:
                if w.upper() = disease:
                        keyword_box.append(w.upper())

이렇게 입력했더니

    if w.upper() = disease:
Syntax Error: invalid syntax: <string>, line 56, pos 30

이런 오류가 떴습니다... 왜 뜨는 걸까요?? ㅠ