python在读取mysql列表时会先显示none才正常输出，如何才能跳过none直接输出表

Question

cur = conn.cursor()

while True:
for i in range(500):
delay(0.1)
sql = 'select * from robot where id=%s;'

  #执行sql
  result = cur.execute(sql, i)
  conn.commit()
  joints = cur.fetchone()
  print(joints)

Answer 1

result = cur.execute(sql, i)
joints = cur.fetchone()
if len(joints)>0:
    print(joints)