python基础实验：模拟音频播放器

假设用程序播放音频。一个播放器对象（mediaplayerobject）创建AudioFile 对象，执行 play 方法。play()方法负责解码音频文件，并播放，其行为可简单描述为audio-file.play()。但解码音频文件，需要根据不同的文件使用不同的算法，wav,mp3,wma,ogg，显然不能用同一种算法解码。如果，要为每种文件定义一个play()方法，那得定义很多少个方法？！而且，随着技术发展，出现新的音频文件格式怎么办，定义多少个方法够用呢？使用继承和多态可以简化设计。思路是这样的，每种格式用 AudioFile 的一个子类表示，如 WavFile、MP3File 等。每个子类都有自己的play()方法，但该方法根据不同子类实现不同的解码算法和播放功能。而播放器对象永远不必知道 AudioFile 指的是哪个子类，播放器只需调用play()方法，让对象的多态机制处理具体的解码播放即可。
本练习涵盖继承、覆盖、多态技术

# polymorphism exercise 
class AudioFile: 
	def __init__(self, filename): 
		if not filename.endswith(filename[-3:]): 
			raise Exception("Invalid file format") 
			self.filename = filename self.ext = filename[-3:]
	def play(self): 
		print("Now an audio file is going to play...{} as {}". format(self.filename, self.ext))
class MP3File(AudioFile): 
	def __init__(self, filename): 
	super().__init__(filename) 
	self.ext = "mp3"
	def play(self): 
	# super().play() 
	print("playing {} as mp3".format(self.filename))
class WavFile(AudioFile): 
	def __init__(self, filename): 
		super().__init__(filename) 
		self.ext = filename[-3:]
	def play(self): 
		print("playing {} as {}".format(self.filename, self.ext))
class OggFile(AudioFile): 
	def __init__(self, filename): super().__init__(filename) 
		self.ext = filename[-3:]
	def play(self): 
		print("playing {} as ogg".format(self.filename))
class FlacFile(AudioFile): 
	def __init__(self,filename): super().__init__(filename) 
		self.ext = filename[-3:]
	def play(self):
		print("playing {} as flac".format(self.filename))
print("===split line ===") 
mp3 = MP3File("myfile.mp3") 
mp3.play() 
print("===split line ===") 
wav = WavFile("myfile.wav") 
wav.play() 
print("===split line ===") 
not_an_mp3 = MP3File("myfile.nothing") 
not_an_mp3.play()
print(’Clearly, it is going to cause decoding error!’) 
print("===split line ===") 
flac = FlacFile("myfile.flac") 
flac.play() 
print(flac.ext) 
print("===split line ===")
print(’----------another split line------------’) 
afile = MP3File("myfile.mp3") 
bfile = WavFile("myfile.wav") 
cfile = FlacFile("myfile.flac")
music_file = [afile, bfile, cfile]
for x in music_file: 
	x.play()

来源：CSDN

作者：Louise_Trender

链接：https://blog.csdn.net/Louise_Trender/article/details/103505887

标签

音频解码

python继承

多态