Как полностью закрыть вкладку с помощью Selenium в Python?

Я бы разместил это в комментарии, но часть кода слишком большая. Я думаю, у вас проблема с отступом. Проверить местонахождение:

browser.switch_to.window(browser.window_handles[1])
browser.close()
browser.switch_to.window(browser.window_handles[0])

Он был перемещен во внешний цикл. Результат тот же, но вкладок открывается гораздо меньше (пробовал на моей машине).

from selenium import webdriver
import os
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
import xlsxwriter
from datetime import datetime
import time
from selenium.common.exceptions import TimeoutException


trade_date_lim = "5/1/2021"


chrome_driver = os.path.abspath('C:/Users/ross/Desktop/chromedriver.exe')
browser = webdriver.Chrome(chrome_driver)


#makes workbook to write to
workbook = xlsxwriter.Workbook('reit_bonds_test.xlsx')
worksheet = workbook.add_worksheet()


stocks = ["PNW", "STWD"]

for stock in stocks:
    browser.get('https://finra-markets.morningstar.com/BondCenter/Default.jsp')
    wait = WebDriverWait(browser, 10)
    #using clicks and send_keys, gets the bond page for a desired stock
    wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR,
                                           '#TabContainer > div > div.rtq-tab-wrap > div.rtq-tab-menus-wrap > ul > li:nth-child(3) > a > span'))).click()
    wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, '#firscreener-cusip'))).send_keys(stock)
    wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR,
                                           "#ms-finra-advanced-search-form > div.ms-finra-advanced-search-btn > input:nth-child(2)"))).click()
    try:
        wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-agreement > input"))).click()
    except TimeoutException:
        pass

    #clicks to sort by earliest date, clicks again to sort by latest maturity
    wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-grid-hd > div > div:nth-child(7) > div"))).click()
    time.sleep(5)
    wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-grid-hd > div > div:nth-child(7) > div"))).click()
    time.sleep(5)
    #gathers all bond offerings on first page
    whole_chart = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-scrollpanel > div.rtq-grid-scroll"))).text

    #gets number of bonds listed on page so we can iterate through them. Some pages have differing number of bonds listed. Most on page is 20
    parent = browser.find_element_by_xpath('//*[@id="ms-finra-search-results"]/div/div[3]/div[1]/div[1]/div[2]/div[2]/div')
    count_divs = len(parent.find_elements_by_xpath("./div"))

    bnd_off_cnt = 1
    row_num = 0
    while row_num < count_divs and bnd_off_cnt < 3:

        #gets values that I'm looking for
        symbol = wait.until(EC.presence_of_element_located((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-scrollpanel > div.rtq-grid-scroll > div > div:nth-child(" + str(row_num + 1) + ") > div:nth-child(3)"))).text
        maturity = wait.until(EC.presence_of_element_located((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-scrollpanel > div.rtq-grid-scroll > div > div:nth-child(" + str(row_num + 1) + ") > div:nth-child(7)"))).text
        moody_rating = wait.until(EC.presence_of_element_located((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-scrollpanel > div.rtq-grid-scroll > div > div:nth-child(" + str(row_num + 1) + ") > div:nth-child(8)"))).text
        sandp_rating = wait.until(EC.presence_of_element_located((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-scrollpanel > div.rtq-grid-scroll > div > div:nth-child(" + str(row_num + 1) + ") > div:nth-child(9)"))).text
        stated_bond_yield = wait.until(EC.presence_of_element_located((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-scrollpanel > div.rtq-grid-scroll > div > div:nth-child(" + str(row_num + 1) + ") > div:nth-child(11)"))).text

        #looks to see if all values are non-empty and if moody rating and sandp rating are not equal to 'WR' and 'NR'
        if symbol.strip() and maturity.strip() and moody_rating.strip() and sandp_rating.strip() and stated_bond_yield.strip() and moody_rating != "WR" and sandp_rating != "NR":
            #bond detail page below
            element = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-finra-search-results > div > div.qs-resultData > div.qs-resultData-body > div.rtq-grid.rtq-grid-auto-h > div.rtq-scrollpanel > div.rtq-grid-scroll > div > div:nth-child(" + str(row_num + 1) + ") > div:nth-child(2) > div > a")))
            element_link = element.get_attribute('href') #gets the link

            #opens window, switches to it and opens the bond detail page
            browser.execute_script("window.open('');")
            time.sleep(3)
            browser.switch_to.window(browser.window_handles[1])
            browser.get(element_link)

            #switch to iframe on second page and clicks it
            wait.until(EC.frame_to_be_available_and_switch_to_it((By.ID, "ms-bond-detail-iframe")))
            wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR,"#tradeHistory_link"))).click()
            #switches to third page
            browser.switch_to.window(browser.window_handles[-1])
            #sleeps for 3 seconds so we know for sure that we are working on right page
            time.sleep(3)


            # get length of table on trades page and iterate through them trying to find the most recent "Trade" status
            bond_trades = wait.until(EC.presence_of_all_elements_located((By.CSS_SELECTOR, "#ms-glossary > div > table > tbody > tr")))
            count = len(bond_trades)


            for trade in range(count):

                bond_trade_status = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-glossary > div > table > tbody > tr:nth-child(" + str(trade + 1) + ") > td:nth-child(4) > div"))).text
                if bond_trade_status == "Trade":
                    bond_last_traded = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-glossary > div > table > tbody > tr:nth-child(" + str(trade + 1) + ") > td:nth-child(1) > div"))).text
                    if bond_last_traded > trade_date_lim:
                        #prior bond yields occasionally don't match the yield that it was last traded at
                        bond_yield = wait.until(EC.element_to_be_clickable((By.CSS_SELECTOR, "#ms-glossary > div > table > tbody > tr:nth-child(" + str(trade + 1) + ") > td:nth-child(7) > div"))).text
                        print(symbol, maturity, bond_yield)
                        bnd_off_cnt += 1
                        break
                    else:
                        continue
                    #test for if we are within X amount of time from today
                    #continue if we are more than that amount of time
                    #exit if we are within time frame and get 'Yield'
                else:
                    continue
        browser.switch_to.window(browser.window_handles[1])
        browser.close()
        browser.switch_to.window(browser.window_handles[0])
        row_num += 1

Я не обратил особого внимания на некоторые проблемы в вашем коде, так как они не обсуждаются.

Попробуйте следующее:

browser.switch_to.window(browser.window_handles[1])
browser.find_element_by_tag_name('body').send_keys(Keys.CONTROL, 'w')
browser.switch_to.window(browser.window_handles[0])

Сначала переключитесь на окно, которое хотите закрыть, затем закройте его с помощью клавиш Control + w и, наконец, перейдите к начальному окну (вкладке)