更新功能/循环问题中的访问令牌（全局变量）

Question

我正在使用Spotify API包装器提取数据。访问令牌（这是全局变量）仅有效1小时，因此我需要在某些定义函数的for循环期间对其进行更新。我尝试使用try / except更新它，但出现以下错误：

  

UnboundLocalError：分配前已引用局部变量“ spotify”。

以下是相关代码：

token = credentials.get_access_token()
spotify = spotipy.Spotify(auth = token)
...

def main():
    ...
    df_af = generate_audio_features_df(track_ids)
    ...

def generate_audio_features_df(track_ids):
    col_list = ['id', 'danceability']
    result = []
    count = 0

    for j in track_ids:
        try:
            r = spotify.audio_features(j)[0]
            features_list = [r['id'], r['danceability']]
            result.append(features_list)
            #display progress
            count += 1
            print("Added ", count, " track")
        except spotipy.client.SpotifyException:
            token = credentials.get_access_token()
            spotify = spotipy.Spotify(auth = token)

    df = pd.DataFrame(data = result, columns = col_list)
    return df

if __name__ == "__init__":
    main()

我希望代码更新令牌并返回循环。