python - list.append()返回空字符串

Question

这是我的第一篇堆栈溢出帖子。如果有任何反馈，我将不胜感激。我正在尝试用champion_name_id中的值填充列表champion_frequency_list。我的嵌套循环似乎返回了一个空列表。有人能帮我理解这个问题吗？

champion_frequency = {235: 19, 202: 26, 145: 3, 523: 5, 360: 3, 67: 1, 236: 5, 498: 1, 21: 2, 96: 3, 22: 18, 110: 1, 51: 3, 429: 1, 81: 2, 104: 1, 2: 1, 115: 1, 14: 1, 61: 1, 875: 1, 31: 1}
champion_name_id = {'1': 'Annie',
                    '10': 'Kayle',
                    '101': 'Xerath',
                    '102': 'Shyvana',
                    '103': 'Ahri',
                    '104': 'Graves',
                    '105': 'Fizz',
                    '106': 'Volibear',
                    '107': 'Rengar',
                    '11': 'MasterYi',
                    '110': 'Varus',
                    '111': 'Nautilus',
                    '112': 'Viktor',
                    '113': 'Sejuani',
                    '114': 'Fiora',
                    '115': 'Ziggs',
                    '117': 'Lulu',
                    '119': 'Draven',
                    '12': 'Alistar',
                    '120': 'Hecarim',
                    '121': 'Khazix',
                    '122': 'Darius',
                    '126': 'Jayce',
                    '127': 'Lissandra',
                    '13': 'Ryze',
                    '131': 'Diana',
                    '133': 'Quinn',
                    '134': 'Syndra',
                    '136': 'AurelionSol',
                    '14': 'Sion',
                    '141': 'Kayn',
                    '142': 'Zoe',
                    '143': 'Zyra',
                    '145': 'Kaisa',
                    '147': 'Seraphine',
                    '15': 'Sivir',
                    '150': 'Gnar',
                    '154': 'Zac',
                    '157': 'Yasuo',
                    '16': 'Soraka',
                    '161': 'Velkoz',
                    '163': 'Taliyah',
                    '164': 'Camille',
                    '17': 'Teemo',
                    '18': 'Tristana',
                    '19': 'Warwick',
                    '2': 'Olaf',
                    '20': 'Nunu',
                    '201': 'Braum',
                    '202': 'Jhin',
                    '203': 'Kindred',
                    '21': 'MissFortune',
                    '22': 'Ashe',
                    '222': 'Jinx',
                    '223': 'TahmKench',
                    '23': 'Tryndamere',
                    '235': 'Senna',
                    '236': 'Lucian',
                    '238': 'Zed',
                    '24': 'Jax',
                    '240': 'Kled',
                    '245': 'Ekko',
                    '246': 'Qiyana',
                    '25': 'Morgana',
                    '254': 'Vi',
                    '26': 'Zilean',
                    '266': 'Aatrox',
                    '267': 'Nami',
                    '268': 'Azir',
                    '27': 'Singed',
                    '28': 'Evelynn',
                    '29': 'Twitch',
                    '3': 'Galio',
                    '30': 'Karthus',
                    '31': 'Chogath',
                    '32': 'Amumu',
                    '33': 'Rammus',
                    '34': 'Anivia',
                    '35': 'Shaco',
                    '350': 'Yuumi',
                    '36': 'DrMundo',
                    '360': 'Samira',
                    '37': 'Sona',
                    '38': 'Kassadin',
                    '39': 'Irelia',
                    '4': 'TwistedFate',
                    '40': 'Janna',
                    '41': 'Gangplank',
                    '412': 'Thresh',
                    '42': 'Corki',
                    '420': 'Illaoi',
                    '421': 'RekSai',
                    '427': 'Ivern',
                    '429': 'Kalista',
                    '43': 'Karma',
                    '432': 'Bard',
                    '44': 'Taric',
                    '45': 'Veigar',
                    '48': 'Trundle',
                    '497': 'Rakan',
                    '498': 'Xayah',
                    '5': 'XinZhao',
                    '50': 'Swain',
                    '51': 'Caitlyn',
                    '516': 'Ornn',
                    '517': 'Sylas',
                    '518': 'Neeko',
                    '523': 'Aphelios',
                    '53': 'Blitzcrank',
                    '54': 'Malphite',
                    '55': 'Katarina',
                    '555': 'Pyke',
                    '56': 'Nocturne',
                    '57': 'Maokai',
                    '58': 'Renekton',
                    '59': 'JarvanIV',
                    '6': 'Urgot',
                    '60': 'Elise',
                    '61': 'Orianna',
                    '62': 'MonkeyKing',
                    '63': 'Brand',
                    '64': 'LeeSin',
                    '67': 'Vayne',
                    '68': 'Rumble',
                    '69': 'Cassiopeia',
                    '7': 'Leblanc',
                    '72': 'Skarner',
                    '74': 'Heimerdinger',
                    '75': 'Nasus',
                    '76': 'Nidalee',
                    '77': 'Udyr',
                    '777': 'Yone',
                    '78': 'Poppy',
                    '79': 'Gragas',
                    '8': 'Vladimir',
                    '80': 'Pantheon',
                    '81': 'Ezreal',
                    '82': 'Mordekaiser',
                    '83': 'Yorick',
                    '84': 'Akali',
                    '85': 'Kennen',
                    '86': 'Garen',
                    '875': 'Sett',
                    '876': 'Lillia',
                    '89': 'Leona',
                    '9': 'Fiddlesticks',
                    '90': 'Malzahar',
                    '91': 'Talon',
                    '92': 'Riven',
                    '96': 'KogMaw',
                    '98': 'Shen',
                    '99': 'Lux'}

champion_frequency_list = []
for key in champion_name_id:
    #print('key', key, 'key-type', type(key))
    for index in range(len(list(champion_frequency.keys()))):
        #print('index',index)
        #print('current champion frequency index', str(list(champion_frequency.keys())[index]), 'type', type(str(list(champion_frequency.keys())[index])))
        #print('is this iteration true?: ', key == str(list(champion_frequency.keys())[index]))
        #print('if true, append to list', champion_name_id[str(key)], 'type', type(champion_name_id[str(key)]))
        champion_name = champion_name_id[str(key)]
        if key == list(champion_frequency.keys())[index]:
            champion_frequency_list.append(champion_name)

print('champion frequency list length', len(champion_frequency_list))
print('champion frequency list', champion_frequency_list)

Answer 1

我不确定这是否是你要找的，但我认为你需要更换

if key == list(champion_frequency.keys())[index]:
            champion_frequency_list.append(champion_name)

使用

if int(key) == list(champion_frequency.keys())[index]:
            champion_frequency_list.append(champion_name)

Answer 2

简而言之，您的键的类型不匹配，因此作为user14654909 notes，您需要将key转换为int，以匹配您从champion_frequency获得的键的类型，从而进行测试：

if int(key) == list(champion_frequency.keys())[index]:

而不是：

if key == list(champion_frequency.keys())[index]:

长长的答案是:这段代码极其复杂和低效；它根本不能从您使用dict中获益。多亏了一个双重嵌套的循环和champion_frequency.keys()的内部重复列表，您正在为一些应该只需要工作的东西做O(n × m²)工作(n是champion_name_id的长度，m是champion_frequency的长度)。除了print之外，整个嵌套循环可以简化为：

champion_frequency_list = [name for champion_id_str, name in champion_name_id.items()
                           if int(champion_id_str) in champion_frequency]

它将为您节省数百个临时list，并从根本上消除与champion_frequency大小相关的所有复杂性(因为简单的成员资格测试在dict中大约是O(1) )。一个简单的例子：

champion_frequency = {... definition omitted for brevity ...}
champion_name_id = {... definition omitted for brevity ...}

champion_frequency_list = []
for key in champion_name_id:
    for index in range(len(list(champion_frequency.keys()))):
        champion_name = champion_name_id[str(key)]
        if int(key) == list(champion_frequency.keys())[index]:
            champion_frequency_list.append(champion_name)

print('champion frequency list length', len(champion_frequency_list))
print('champion frequency list', champion_frequency_list)

champion_frequency_list_simple = [name for champion_id_str, name in champion_name_id.items()
                                  if int(champion_id_str) in champion_frequency]
print('Simple champion frequency list', champion_frequency_list_simple)
print('Is simple solution result identical?', champion_frequency_list == champion_frequency_list_simple)

Try it online!