本文實(shí)例講述了Python實(shí)現(xiàn)擴(kuò)展內(nèi)置類型的方法。分享給大家供大家參考，具體如下：
簡(jiǎn)介
除了實(shí)現(xiàn)新的類型的對(duì)象方式外，有時(shí)我們也可以通過(guò)擴(kuò)展Python內(nèi)置類型，從而支持其它類型的數(shù)據(jù)結(jié)構(gòu)，比如為列表增加隊(duì)列的插入和刪除的方法。本文針對(duì)此問(wèn)題，結(jié)合實(shí)現(xiàn)集合功能的實(shí)例，介紹了擴(kuò)展Python內(nèi)置類型的兩種方法：通過(guò)嵌入內(nèi)置類型來(lái)擴(kuò)展類型和通過(guò)子類方式擴(kuò)展類型。
通過(guò)嵌入內(nèi)置類型擴(kuò)展
下面例子通過(guò)將list對(duì)象作為嵌入類型，實(shí)現(xiàn)集合對(duì)象，并增加了一下運(yùn)算符重載。這個(gè)類知識(shí)包裝了Python的列表，以及附加的集合運(yùn)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(guò)子類方式擴(kuò)展類型
從Python2.2開(kāi)始，所有內(nèi)置類型都能直接創(chuàng)建子類，如list，str，dict以及tuple。這樣可以讓你通過(guò)用戶定義的class語(yǔ)句，定制或擴(kuò)展內(nèi)置類型：建立類型名稱的子類并對(duì)其進(jìn)行定制。類型的子類型實(shí)例，可用在原始的內(nèi)置類型能夠出現(xiàn)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)
希望本文所述對(duì)大家Python程序設(shè)計(jì)有所幫助。
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