title: How to fix "TypeError: can only concatenate list (not "str") to list" Error
body: <p>I want my function <code>getPlaylists(a,b,c)</code> to take values from lists a,b, and c and run until all elements in each list are used.</p>
  
  <p>Specifically, I'd like to setup <code>getPlaylists(a,b,c)</code> so it runs <code>getPlaylists(a[0],b[0],c[0])</code> then <code>getPlaylists(a[1],b[1],c[1])</code> etc... until it completes all values in lists a,b, and c.</p>
  
  <p>I have tried running <code>getPlaylists(a[0:],b[0:],c[0:])</code> and it gives me the error:</p>
  
  <blockquote>
    <p>"TypeError: can only concatenate list (not "str") to list"</p>
  </blockquote>
  
  <p>I have also tried running <code>getPlaylists(a[0],b[0],c[0])</code> followed by <code>getPlaylists(a[1],b[1],c[1])</code> in the following line. Only the first function prints successfully.</p>
  
  <pre><code>import spotipy
  from spotipy.oauth2 import SpotifyClientCredentials
  
  
  def getPlaylists(a,b,c):
      client_credentials_manager = SpotifyClientCredentials(client_id=a, client_secret=b)
      sp = spotipy.Spotify(client_credentials_manager=client_credentials_manager)
  
      playlists = sp.user_playlists(c)
  
      while playlists:
          for i, playlist in enumerate(playlists['items']):
              print("%4d %s %s" % (i + 1 + playlists['offset'], playlist['uri'],  playlist['name']))
          if playlists['next']:
              playlists = sp.next(playlists)
          else:
              playlists = None
  a= ["7ce6355bc7a34c659b6ce0b6a0c53395","a15e38973eb64f9bba30258a9dde407d"]
  b= ["026081a8e1a544dbbcc2bf8a373f3088","8af7eaa281dc49a58d08e46adf06e637"]
  c= ["121147088","20mc3a9w582vc7a7o5cjm03d8"]
  
  getPlaylists(a[0:],b[0:],c[0:])
  </code></pre>
  
  <p>I expected all the playlists from each spotify account to print. However, when I format my code as I did above, I get the following errors:</p>
  
  <blockquote>
  <pre><code>Traceback (most recent call last):
    File "C:/Users/19083/AppData/Local/Programs/Python/Python37-32/SpotifyTest2_9.18.py", line 22, in &lt;module&gt;
      getPlaylists(a[0:],b[0:],c[0:])
    File "C:/Users/19083/AppData/Local/Programs/Python/Python37-32/SpotifyTest2_9.18.py", line 9, in getPlaylists
      playlists = sp.user_playlists(c)
    File "C:\Users\19083\AppData\Local\Programs\Python\Python37-32\lib\site-packages\spotipy\client.py", line 366, in user_playlists
      offset=offset)
    File "C:\Users\19083\AppData\Local\Programs\Python\Python37-32\lib\site-packages\spotipy\client.py", line 146, in _get
      return self._internal_call('GET', url, payload, kwargs)
    File "C:\Users\19083\AppData\Local\Programs\Python\Python37-32\lib\site-packages\spotipy\client.py", line 100, in _internal_call
      headers = self._auth_headers()
    File "C:\Users\19083\AppData\Local\Programs\Python\Python37-32\lib\site-packages\spotipy\client.py", line 90, in _auth_headers
      token = self.client_credentials_manager.get_access_token()
    File "C:\Users\19083\AppData\Local\Programs\Python\Python37-32\lib\site-packages\spotipy\oauth2.py", line 57, in get_access_token
      token_info = self._request_access_token()
    File "C:\Users\19083\AppData\Local\Programs\Python\Python37-32\lib\site-packages\spotipy\oauth2.py", line 67, in _request_access_token
      auth_header = base64.b64encode(str(self.client_id + ':' + self.client_secret).encode())
  TypeError: can only concatenate list (not "str") to list
  </code></pre>
  </blockquote>
  
  <pre><code>
  </code></pre>