Assuming you are trying to rely on the preceding a element, use following-sibling, example:
//a/following-sibling::b
Python code:
b = driver.find_element_by_xpath("//a/following-sibling::b")
print(b.text)
If you want multiple b tags having a as a preceding element:
for b in driver.find_elements_by_xpath("//a/following-sibling::b"):
print(b.text)
Solution provided after chatting:
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
driver = webdriver.Chrome()
driver.get("http://www.drugs.com/drug-class/laxatives.html?condition_id=&generic=0&sort=rating&order=desc")
# Wait for the table list to load
table = WebDriverWait(driver, 10).until(EC.presence_of_element_located((By.CSS_SELECTOR, "table.data-list")))
for b in table.find_elements_by_css_selector("tr td > a[href] > b"):
print(b.text)