title: Empty iframe in Selenium yet filled in browser (python)
body: <p>I'm trying to control Spotify's browser player. All of the controls are put inside iframe sections.</p>
  
  <p><strong>Problem:</strong> The iframes are EMPTY in the Selenium WebDriver object. Yet, the iframes are filled with the correct content in the ACTUAL browser.</p>
  
  <p><strong>Code sample:</strong></p>
  
  <pre><code>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
  
  import time
  
  username = 'myusername'
  base_url = 'https://play.spotify.com/user/spotifydiscover/playlist/76HML2OQXigkyKopqYkeng'
  
  browser = None
  
  def login():
      global browser
      password = input("Password: ")
      browser = webdriver.Firefox()
      browser.get(base_url)
  
      browser.find_element_by_id('has-account').click()
  
      browser.find_element_by_id('login-usr').clear()
      browser.find_element_by_id('login-usr').send_keys(username)
  
      browser.find_element_by_id('login-pass').clear()
      browser.find_element_by_id('login-pass').send_keys(password)
      browser.find_element_by_id('login-pass').submit()
  
  def next_track():
      global browser
      wrapper = browser.find_element_by_id("section-collection")
      print(wrapper.get_attribute('innerHTML').encode('utf-8'))
      iframe = wrapper.find_element_by_tag_name('iframe')
      print(iframe.get_attribute('innerHTML').encode('utf-8'))
      sub = browser.switch_to_frame(iframe)
      sub.find_element_by_id('next').click()
  
  def test():
      login()
      time.sleep(14) # Adjusted until page is 100% fully loaded
      next_track()
      time.sleep(40)
  </code></pre>