蟒蛇 - 似乎无法从孩子

Question

这里调用父类的方法，是我的代码：

from mutagen.easyid3 import EasyID3 
from mutagen import File 

class MusicFile: 
    """A class representing a particular music file. 

    Children that are intended to be instantiated must initialize fields for 
    the getters that exist in this class. 
    """ 

    def __init__(self, location): 
     self.location = location 

    def getLocation(): 
     return self.location 

    def getArtist(): 
     return self.artist 

    def getAlbum(): 
     return self.album 

    def getTitle(): 
     return self.title 

############################################################################### 


class LossyMusicFile(MusicFile): 
    """A class representing a lossy music file. 

    Contains all functionality required by only lossy music files. To date, that 
    is processing bitrates into a standard number and returning format with 
    bitrate. 
    """ 
    def __init__(self, location): 
     super().__init__(location) 

    def parseBitrate(br): 
     """Takes a given precise bitrate value and rounds it to the closest 
     standard bitrate. 

     Standard bitrate varies by specific filetype and is to be set by the 
     child. 
     """ 
     prevDiff=999999999 
     for std in self.bitrates: 
      # As we iterate through the ordered list, difference should be 
      # getting smaller and smaller as we tend towards the best rounding 
      # value. When the difference gets bigger, we know the previous one 
      # was the closest. 
      diff = abs(br-std) 
      if diff>prevDiff: 
       return prev 
      prevDiff = diff 
      prev = std 

    def getFormat(): 
     """Return the format as a string. 

     look like the format name (a class variable in the children), followed 
     by a slash, followed by the bitrate in kbps (an instance variable in the 
     children). a 320kbps mp3 would be 'mp3/320'. 
     """ 
     return self.format + '/' + self.bitrate 


############################################################################### 

class Mp3File(LossyMusicFile): 
    """A class representing an mp3 file.""" 

    format = "mp3" 

    # Threw a large value on the end so parseBitrate() can iterate after the end 
    bitrates = (32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 
       128000, 160000, 192000, 224000, 256000, 320000, 999999) 

    def __init__(self, location): 
     super().__init__(location) 

     id3Info = EasyID3(location) 
     self.artist = id3Info['artist'][0] 
     self.album = id3Info['album'][0] 
     self.title = id3Info['title'][0] 
     # Once we set it here, bitrate shall be known in kbps 
     self.bitrate = (self.parseBitrate(File(location).info.bitrate))/1000 

现在，当我尝试实例化一个Mp3File，它给了我一个错误上的最后一行Mp3File.__init__()：

line 113, in __init__ 
self.bitrate = (self.parseBitrate(File(location).info.bitrate))/1000 
NameError: name 'parseBitrate' is not defined 

然而，在我看来，它应该没有找对方法在Mp3File，然后寻找父类，LossyMusicFile，如果它确实存在的方法。

我试着将这一行改为self.bitrate = (super().parseBitrate(File(location).info.bitrate))/1000，这样它会明确地使用父类的方法，但是我得到了同样的错误。这是怎么回事？

如果以前有人问过这个问题，或者是一个愚蠢的问题，但是我找不到它，当我搜索时，我实际上是愚蠢的。

Answer 1

所有的实例方法都必须具有self作为第一个参数。这里发生的是，在parseBitrate()中，您将self更名为br。您需要parseBitrate(self, br)才能接受比特率。您还需要在其他方法（如getFormat()）中将self添加到参数列表中。

1. 您的代码使用thisVariableNamingStyle它违背了Python的官方风格文档PEP 8。
2. MusicFile不会继承关闭object。 您只能在“新风格的类”中调用从更高类继承的方法。为了让你的班级“新式”，你必须继承object。

另外，得到一个像PyCharm这样的IDE，可以在将来自动提醒你这些错误。