我没有＆＃39;知道为什么我的for循环没有返回任何东西

Question

我没有＆＃39;知道为什么我的for循环没有返回任何内容#table tame是sql中的表，它应该以下面的格式从sql表返回每个项目。

def count_columns(table_name):
    cur.execute("SELECT * FROM " + table_name)
    for row in cur.fetchall():
        if len(row) == "2":
            print("ID: ", row,[0], "Category: ", row[1])
        elif len(row) == "3":
            print("ID: ", row,[0], "Range: ", row[1], "Category: ", row[2])
        elif len(row) == "4":
            print("ID: ", row,[0], "Systolic: ", row[1], "Diastolic: ", row[2], "Category: ", row[3])