使用動態繼承類來指定對象的特徵

Question

我有一個封裝具有某些特徵的網絡配置文件的對象。例如，我的檔案有連接並根據它，它可以或不可以有IP選項（靜態或DHCP）。

所以，我的第一次嘗試使用從字典延伸的正常類，並添加了一些輔助功能：

class Profile(dict): 
    IP_CONNECTIONS = ('ethernet', 'wireless', 'pppoe') 
    def is_ethernet(self): return self['Connection'] == 'ethernet' 
    def is_wireless(self): return self['Connection'] == 'wireless' 
    def is_wireless_adhoc(self): return self.is_wireless() and 'AdHoc' in self 
    def has_ip(self) 
     return self['Connection'] in self.IP_CONNECTIONS 
    def has_ip_static(self) 
     if not self.has_ip(): 
      return False 
     if self.is_ipv4(): 
      return self['IP'] == 'static' 
     if self.is_ipv6(): 
      return self['IP6'] == 'static' 
     return False 
    def has_ip_dhcp(self): 
     if not self.has_ip(): 
      return False 
     if self.is_ipv4(): 
      return self['IP'] == 'dhcp' 
     if self.is_ipv6(): 
      return self['IP6'] == 'dhcp' or self['IP6'] == 'dhcp-noaddr' 
     return False 
    def is_ipv4(self): return self.has_ip() and 'IP' in self 
    def is_ipv6(self): return self.has_ip() and 'IP6' in self 
    def get_client(self): 
     if self.has_ip_dhcp() and 'DHCPClient' in self: 
      return self['DHCPClient'] 
     return None 

這個工作，但我有一個巨大的類與很多is_*和has_*特徵功能。他們中的大多數只會用於非常具體的配置文件，並且大多數時候會返回False。

然後它跨過我的腦海，我可以使用繼承來描述特徵。

在嘗試並未能實現元類之後，因爲在調用__new__方法時數據尚不可用。我想出了這樣的事情：

def load_profile(filename): 
    data = _read_profile(filename) 
    bases = _classify_profile(data) 
    baseclass = type('Profile', bases, {}) 
    return baseclass(data) 

class IP: 
    CONNECTIONS = ('ethernet', 'wireless') 
class IPv4(IP): 
    def is_static(self): 
     return self['IP'] == 'static' 
class IPv6(IP): 
    def is_static(self): 
     return self['IP6'] == 'static' 
class DHCP: 
    def get_client(self): 
     return self['DHCPClient'] if 'DHCPClient' in self else None 

class Wireless: 
    def is_adhoc(self): 
     return 'AdHoc' in self 

def _classify_profile(data): 
    classes = [dict] 

    if data['Connection'] == 'wireless': 
     classes.append(Wireless) 
    if data['Connection'] in IP.CONNECTIONS: 
     if 'IP' in data: 
      classes.append(IPv4) 
      if data['IP'] == 'dhcp': 
       classes.append(DHCP) 
     if 'IP6' in data: 
      classes.append(IPv6) 
      if data['IP6'] == 'dhcp' or data['IP6'] == 'dhcp-noaddr': 
       classes.append(DHCP) 

    return tuple(classes) 

我在做profile.has_ip()之前，現在我只是isinstance(profile, IP)測試。這在我看來更加明確，責任分工很好。

問題：這是實現動態繼承的好方法嗎？這樣做的pythonic方式是什麼？

提前致謝！

Answer 1

我真的不知道你的動態繼承的意思，但我會寫這樣說：

base_classes = [] 

class IP(dict): 
    CONNECTIONS = ('ethernet', 'wireless') 
    def is_static(self): 
     raise NotImplementedError('To be implemented in subclasses.') 
    @classmethod 
    def wants_the_meaningful_named_data(cls, data): 
     return False 
base_classes.append(IP) 

class IPv4(IP): 
    def is_static(self): 
     return self['IP'] == 'static' 
    @classmethod 
    def wants_the_meaningful_named_data(cls, data): 
     return data['Connection'] in cls.CONNECTIONS and 'IP' in data 
base_classes.append(IPv4) 

class IPv6(IP): 
    def is_static(self): 
     return self['IP6'] == 'static' 
    @classmethod 
    def wants_the_meaningful_named_data(cls, data): 
     return data['Connection'] in cls.CONNECTIONS and 'IP6' in data 
base_classes.append(IPv6) 

def load_profile(filename): 
    data = _read_profile(filename) 
    for base_class in base_classes: 
     if base_class.wants_the_meaningful_named_data(data): 
      return base_class(data) 
    return dict(data) 

像這樣的事情會是什麼，我喜歡。我不認爲有必要進入元類。