{"id":6519,"date":"2018-03-17T14:07:44","date_gmt":"2018-03-17T06:07:44","guid":{"rendered":"https:\/\/kyle.ai\/blog\/?p=6519"},"modified":"2018-03-17T14:08:36","modified_gmt":"2018-03-17T06:08:36","slug":"%e7%90%86%e8%a7%a3-python-%e4%b8%ad%e7%9a%84-super","status":"publish","type":"post","link":"https:\/\/kyle.ai\/blog\/6519.html","title":{"rendered":"\u7406\u89e3 Python \u4e2d\u7684 super"},"content":{"rendered":"

\u8981\u8c08\u8bba super\uff0c\u9996\u5148\u6211\u4eec\u5e94\u8be5\u65e0\u89c6 “super” \u8fd9\u4e2a\u540d\u5b57\u5e26\u7ed9\u6211\u4eec\u7684\u5e72\u6270\u3002<\/p>\n

\u4e0d\u8981\u4e00\u8bf4\u5230 super \u5c31\u60f3\u5230\u7236\u7c7b\uff01super \u6307\u7684\u662f MRO \u4e2d\u7684\u4e0b\u4e00\u4e2a\u7c7b\uff01
\n\u4e0d\u8981\u4e00\u8bf4\u5230 super \u5c31\u60f3\u5230\u7236\u7c7b\uff01super \u6307\u7684\u662f MRO \u4e2d\u7684\u4e0b\u4e00\u4e2a\u7c7b\uff01
\n\u4e0d\u8981\u4e00\u8bf4\u5230 super \u5c31\u60f3\u5230\u7236\u7c7b\uff01super \u6307\u7684\u662f MRO \u4e2d\u7684\u4e0b\u4e00\u4e2a\u7c7b\uff01<\/p>\n

\u4e00\u8bf4\u5230 super \u5c31\u60f3\u5230\u7236\u7c7b\u8fd9\u662f\u521d\u5b66\u8005\u5f88\u5bb9\u6613\u72af\u7684\u4e00\u4e2a\u9519\u8bef\uff0c\u4e5f\u662f\u6211\u5f53\u5e74\u72af\u7684\u9519\u8bef\u3002 \u5fd8\u8bb0\u4e86\u8fd9\u4ef6\u4e8b\u4e4b\u540e\uff0c\u518d\u53bb\u770b\u8fd9\u7bc7\u6587\u7ae0\uff1aPython\u2019s super() considered super! <\/a>\u8fd9\u662f Raymond Hettinger \u5199\u7684\u4e00\u7bc7\u6587\u7ae0\uff0c\u4e5f\u662f\u5168\u4e16\u754c\u516c\u8ba4\u7684\u5bf9 super \u8bb2\u89e3\u6700\u900f\u5f7b\u7684\u4e00\u7bc7\u6587\u7ae0\uff0c\u51e1\u662f\u8ba8\u8bba super \u90fd\u4e00\u5b9a\u4f1a\u63d0\u5230\u5b83\uff08\u5f53\u7136\u8fd8\u6709\u4e00\u7bc7 Python’s Super Considered Harmful\uff09\u3002<\/p>\n

\u5982\u679c\u4e0d\u60f3\u770b\u957f\u7bc7\u5927\u8bba\u5c31\u53bb\u770b\u8fd9\u4e2a\u7b54\u6848<\/a>\uff0csuper \u5176\u5b9e\u5e72\u7684\u662f\u8fd9\u4ef6\u4e8b\uff1a<\/p>\n

\r\ndef super(cls, inst):\r\n    mro = inst.__class__.mro()\r\n    return mro[mro.index(cls) + 1]\r\n<\/pre>\n
\u4e24\u4e2a\u53c2\u6570 cls \u548c inst \u5206\u522b\u505a\u4e86\u4e24\u4ef6\u4e8b\uff1a<\/p>\n
    \n
  1. inst \u8d1f\u8d23\u751f\u6210 MRO \u7684 list<\/li>\n
  2. \u901a\u8fc7 cls \u5b9a\u4f4d\u5f53\u524d MRO \u4e2d\u7684 index, \u5e76\u8fd4\u56de mro[index + 1]<\/li>\n<\/ol>\n
    \u8fd9\u4e24\u4ef6\u4e8b\u624d\u662f super \u7684\u5b9e\u8d28\uff0c\u4e00\u5b9a\u8981\u8bb0\u4f4f\uff01<\/p>\n
    MRO \u5168\u79f0 Method Resolution Order\uff0c\u5b83\u4ee3\u8868\u4e86\u7c7b\u7ee7\u627f\u7684\u987a\u5e8f\u3002\u540e\u9762\u8be6\u7ec6\u8bf4\u3002<\/p>\n
    \u4e3e\u4e2a\u4f8b\u5b50<\/p>\n
    \r\nclass Root(object):\r\n    def __init__(self):\r\n        print("this is Root")\r\n\r\nclass B(Root):\r\n    def __init__(self):\r\n        print("enter B")\r\n        # print(self)  # this will print <__main__.D object at 0x...>\r\n        super(B, self).__init__()\r\n        print("leave B")\r\n\r\nclass C(Root):\r\n    def __init__(self):\r\n        print("enter C")\r\n        super(C, self).__init__()\r\n        print("leave C")\r\n\r\nclass D(B, C):\r\n    pass\r\n\r\nd = D()\r\nprint(d.__class__.__mro__)\r\n<\/pre>\n
    \u8f93\u51fa<\/p>\n
    \r\nenter B\r\nenter C\r\nthis is Root\r\nleave C\r\nleave B\r\n(<class '__main__.D'>, <class '__main__.B'>, <class '__main__.C'>, <class '__main__.Root'>, <type 'object'>)\r\n<\/pre>\n
    \u77e5\u9053\u4e86 super \u548c\u7236\u7c7b\u5176\u5b9e\u6ca1\u6709\u5b9e\u8d28\u5173\u8054\u4e4b\u540e\uff0c\u6211\u4eec\u5c31\u4e0d\u96be\u7406\u89e3\u4e3a\u4ec0\u4e48 enter B \u4e0b\u4e00\u53e5\u662f enter C \u800c\u4e0d\u662f this is Root\uff08\u5982\u679c\u8ba4\u4e3a super \u4ee3\u8868\u201c\u8c03\u7528\u7236\u7c7b\u7684\u65b9\u6cd5\u201d\uff0c\u4f1a\u60f3\u5f53\u7136\u7684\u8ba4\u4e3a\u4e0b\u4e00\u53e5\u5e94\u8be5\u662fthis is Root\uff09\u3002\u6d41\u7a0b\u5982\u4e0b\uff0c\u5728 B \u7684 __init__ \u51fd\u6570\u4e2d\uff1a<\/p>\n
    \r\nsuper(B, self).__init__()\r\n<\/pre>\n
    \u9996\u5148\uff0c\u6211\u4eec\u83b7\u53d6 self.__class__.__mro__\uff0c\u6ce8\u610f\u8fd9\u91cc\u7684 self \u662f D \u7684 instance \u800c\u4e0d\u662f B \u7684<\/p>\n
    \r\n(<class '__main__.D'>, <class '__main__.B'>, <class '__main__.C'>, <class '__main__.Root'>, <type 'object'>)\r\n<\/pre>\n
    \u7136\u540e\uff0c\u901a\u8fc7 B \u6765\u5b9a\u4f4d MRO \u4e2d\u7684 index\uff0c\u5e76\u627e\u5230\u4e0b\u4e00\u4e2a\u3002\u663e\u7136 B \u7684\u4e0b\u4e00\u4e2a\u662f C\u3002\u4e8e\u662f\uff0c\u6211\u4eec\u8c03\u7528 C \u7684 __init__\uff0c\u6253\u51fa enter C\u3002<\/p>\n
    \u987a\u4fbf\u8bf4\u4e00\u53e5\u4e3a\u4ec0\u4e48 B \u7684 __init__ \u4f1a\u88ab\u8c03\u7528\uff1a\u56e0\u4e3a D \u6ca1\u6709\u5b9a\u4e49 __init__\uff0c\u6240\u4ee5\u4f1a\u5728 MRO \u4e2d\u627e\u4e0b\u4e00\u4e2a\u7c7b\uff0c\u53bb\u67e5\u770b\u5b83\u6709\u6ca1\u6709\u5b9a\u4e49 __init__\uff0c\u4e5f\u5c31\u662f\u53bb\u8c03\u7528 B \u7684 __init__\u3002<\/p>\n
    \u5176\u5b9e\u8fd9\u4e00\u5207\u903b\u8f91\u8fd8\u662f\u5f88\u6e05\u6670\u7684\uff0c\u5173\u952e\u662f\u7406\u89e3 super \u5230\u5e95\u505a\u4e86\u4ec0\u4e48\u3002<\/p>\n
    \u4e8e\u662f\uff0cMRO \u4e2d\u7c7b\u7684\u987a\u5e8f\u5230\u5e95\u662f\u600e\u4e48\u6392\u7684\u5462\uff1fPython\u2019s super() considered super!\u4e2d\u5df2\u7ecf\u6709\u5f88\u597d\u7684\u89e3\u91ca\uff0c\u6211\u7ffb\u8bd1\u4e00\u4e0b\uff1a<\/p>\n