折磨写我拿不到这个a值是什么原因

Question

错误
a = 16
for i in range(17):
    a -= i
    self.driver.find_element(By.CSS_SELECTOR,
                             ".unshow-out:nth-child(2) .unshow-right-item:nth-child('a')").click()
    time.sleep(2)

正确

self.driver.find_element(By.CSS_SELECTOR, ".unshow-out:nth-child(2) .unshow-right-item:nth-child(16)").click()

Answer 1

self.driver.find_element(By.CSS_SELECTOR,
                             ".unshow-out:nth-child(2) .unshow-right-item:nth-child("+a+")").click()