'合并'Python中的两个对象

Question

我想弄清楚如何将两个对象合并在一起。我的目标是合并两个Album对象（下面的代码）。只有Album对象的'title'参数相同时，我需要能够合并多个Album对象的tracks参数（它们是列表）。

基本上，如果我有一个Album对象，其中tracks参数的长度为1，并且其他相册对象，其中tracks参数的长度也为1，新的或更新的单数Album对象需要具有tracks参数长度为2.

我已经发布我的代码以显示如何定义对象。

提前致谢！

编辑：因为tracks参数列表中的每个元素都是歌曲的名称，所以我想保留相同的元素并将它们放入新的或更新的tracks参数中。我不需要改变元素的数量，而需要将每个对象的确切元素放入这个“新”对象中。

class Album(object) : 
    def __init__(self, artist, title, tracks = None) : 
     tracks = [] 
     self.artist = artist 
     self.title = title 
     self.tracks = tracks 

    def add_track(self, track) : 
     self.track = track 
     (self.tracks).append(track) 
     print "The track %s was added." % (track) 

    def __str__(self) : 
     if len(self.tracks) == 1 : 
      return "Artist: %s, Album: %s [" % (self.artist, self.title) + "1 Track]" 
     return "Artist: %s, Album: %s [" % (self.artist, self.title) + str(len(self.tracks)) + " Tracks]" 

Answer 1

合并算法必须知道类的内部数据结构。所以，把合并代码放在类里似乎是合乎逻辑的。下面的代码这是否和允许两张专辑被简单地合并增加它们（album1 + album2）：

class Album(object) : 
    def __init__(self, artist, title, tracks = None) : 
     self.artist = artist 
     self.title = title 
     self.tracks = tracks 

    def add_track(self, track) : 
     self.track = track 
     (self.tracks).append(track) 
     print "The track %s was added." % (track) 

    def __str__(self) : 
     if len(self.tracks) == 1 : 
      return "Artist: %s, Album: %s [" % (self.artist, self.title) + "1 Track]" 
     return "Artist: %s, Album: %s [" % (self.artist, self.title) + str(len(self.tracks)) + " Tracks]" 

    def __add__(self, other): 
     if self.artist != other.artist or self.title != other.title: 
      raise ValueError("Albums are incommensurable") 
     return Album(self.artist, self.title, self.tracks + other.tracks) 

这是用来如下：

>>> a = Album('Joe', "Joe's First", tracks=['Beer', 'Trucks']) 
>>> b = Album('Joe', "Joe's First", tracks=['Bourbon', 'Tequila']) 
>>> complete = a + b 
>>> print complete 
Artist: Joe, Album: Joe's First [4 Tracks] 
>>> complete.tracks 
['Beer', 'Trucks', 'Bourbon', 'Tequila'] 

Answer 2

关于让你不需要是相同的元素你只需要if条件检查之前加入音轨：

def add_track(self, track) : 
    self.track = track 
    if track not in (self.tracks) : 
     (self.tracks).append(track) 
    else : 
     raise ValueError("duplicate track") 
    print "The track %s was added." % (track) 

Answer 3

def merge_albums(album1, album2): 
    if not album1.artist == album2.artist and \ 
      album1.title == album2.title: 
     raise SomeException("Albums don't match") 
    new_tracks = list(set(album1.tracks + album2.tracks)) 
    return Album(album1.artist, album1.title, new_tracks) 

Answer 4

我我认为只有在艺术家和标题相同的情况下，你才会合并专辑的曲目。要做到这一点的方法之一是通过如下定义自己的合并功能：

class Album(object) : 
    def __init__(self, artist, title, tracks = None) : 
     tracks = [] 
     self.artist = artist 
     self.title = title 
     self.tracks = tracks 

    def add_track(self, track) : 
     self.track = track 
     (self.tracks).append(track) 
     print "The track %s was added." % (track) 

    def merge(self, album): 
     if (type(self)==type(album)): 
      if self.artist == album.artist and self.title==album.title: 
       self.tracks.extend(album.tracks) 
      else: 
       print "cannot merge albums, artists or titles are not same" 
     else: 
      print "Invalid object types, cannot merge" 
    def __str__(self) : 
     if len(self.tracks) == 1 : 
      return "Artist: %s, Album: %s [" % (self.artist, self.title) + "1 Track]" 
     return "Artist: %s, Album: %s [" % (self.artist, self.title) + \ 
       str(len(self.tracks)) + " Tracks]" 

然后，如果你有专辑，你可以调用a.merge（二）合并后a.tracks应包含合并的轨道。您需要根据需要进行其他更改。