本文實例講述了Python實現擴展內置類型的方法。分享給大家供大家參考，具體如下：

簡介

除了實現新的類型的對象方式外，有時我們也可以通過擴展Python內置類型，從而支持其它類型的數據結構，比如為列表增加隊列的插入和刪除的方法。本文針對此問題，結合實現集合功能的實例，介紹了擴展Python內置類型的兩種方法：通過嵌入內置類型來擴展類型和通過子類方式擴展類型。

通過嵌入內置類型擴展

下面例子通過將list對象作為嵌入類型，實現集合對象，并增加了一下運算符重載。這個類知識包裝了Python的列表，以及附加的集合運算。

class Set:  def __init__(self, value=[]): # Constructor    self.data = [] # Manages a list    self.concat(value)  def intersect(self, other): # other is any sequence    res = [] # self is the subject    for x in self.data:      if x in other: # Pick common items        res.append(x)    return Set(res) # Return a new Set  def union(self, other): # other is any sequence    res = self.data[:] # Copy of my list    for x in other: # Add items in other      if not x in res:        res.append(x)    return Set(res)  def concat(self, value): # value: list, Set...    for x in value: # Removes duplicates      if not x in self.data:        self.data.append(x)  def __len__(self):     return len(self.data) # len(self)  def __getitem__(self, key): return self.data[key] # self[i]  def __and__(self, other):  return self.intersect(other) # self & other  def __or__(self, other):  return self.union(other) # self | other  def __repr__(self):     return 'Set:' + repr(self.data) # print()if __name__ == '__main__':  x = Set([1, 3, 5, 7])  print(x.union(Set([1, 4, 7]))) # prints Set:[1, 3, 5, 7, 4]  print(x | Set([1, 4, 6])) # prints Set:[1, 3, 5, 7, 4, 6]

通過子類方式擴展類型

從Python2.2開始，所有內置類型都能直接創建子類，如list，str，dict以及tuple。這樣可以讓你通過用戶定義的class語句，定制或擴展內置類型：建立類型名稱的子類并對其進行定制。類型的子類型實例，可用在原始的內置類型能夠出現的任何地方。

class Set(list):  def __init__(self, value = []):   # Constructor    list.__init__([])        # Customizes list    self.concat(value)        # Copies mutable defaults  def intersect(self, other):     # other is any sequence    res = []             # self is the subject    for x in self:      if x in other:        # Pick common items        res.append(x)    return Set(res)         # Return a new Set  def union(self, other):       # other is any sequence    res = Set(self)         # Copy me and my list    res.concat(other)    return res  def concat(self, value):       # value: list, Set . . .    for x in value:         # Removes duplicates      if not x in self:        self.append(x)  def __and__(self, other): return self.intersect(other)  def __or__(self, other): return self.union(other)  def __repr__(self):    return 'Set:' + list.__repr__(self)if __name__ == '__main__':  x = Set([1,3,5,7])  y = Set([2,1,4,5,6])  print(x, y, len(x))  print(x.intersect(y), y.union(x))  print(x & y, x | y)  x.reverse(); print(x)