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深入 Python :Dive Into Python 中文版Python 从新手到专家 [Dip_5.4b_CPyUG_Release] |
这一章,和此后的许多章,均讨论了面向对象的 Python 程序设计。
下面是一个完整的,可运行的 Python 程序。请阅读模块、类和函数的 doc strings,可以大概了解这个程序所做的事情和工作情况。像平时一样,不用担心你不理解的东西,这就是本章其它部分将告诉你的内容。
如果您还没有下载本书附带的样例程序, 可以 下载本程序和其他样例程序。
"""Framework for getting filetype-specific metadata. Instantiate appropriate class with filename. Returned object acts like a dictionary, with key-value pairs for each piece of metadata. import fileinfo info = fileinfo.MP3FileInfo("/music/ap/mahadeva.mp3") print "\\n".join(["%s=%s" % (k, v) for k, v in info.items()]) Or use listDirectory function to get info on all files in a directory. for info in fileinfo.listDirectory("/music/ap/", [".mp3"]): ... Framework can be extended by adding classes for particular file types, e.g. HTMLFileInfo, MPGFileInfo, DOCFileInfo. Each class is completely responsible for parsing its files appropriately; see MP3FileInfo for example. """ import os import sys from UserDict import UserDict def stripnulls(data): "strip whitespace and nulls" return data.replace("\00", "").strip() class FileInfo(UserDict): "store file metadata" def __init__(self, filename=None): UserDict.__init__(self) self["name"] = filename class MP3FileInfo(FileInfo): "store ID3v1.0 MP3 tags" tagDataMap = {"title" : ( 3, 33, stripnulls), "artist" : ( 33, 63, stripnulls), "album" : ( 63, 93, stripnulls), "year" : ( 93, 97, stripnulls), "comment" : ( 97, 126, stripnulls), "genre" : (127, 128, ord)} def __parse(self, filename): "parse ID3v1.0 tags from MP3 file" self.clear() try: fsock = open(filename, "rb", 0) try: fsock.seek(-128, 2) tagdata = fsock.read(128) finally: fsock.close() if tagdata[:3] == "TAG": for tag, (start, end, parseFunc) in self.tagDataMap.items(): self[tag] = parseFunc(tagdata[start:end]) except IOError: pass def __setitem__(self, key, item): if key == "name" and item: self.__parse(item) FileInfo.__setitem__(self, key, item) def listDirectory(directory, fileExtList): "get list of file info objects for files of particular extensions" fileList = [os.path.normcase(f) for f in os.listdir(directory)] fileList = [os.path.join(directory, f) for f in fileList if os.path.splitext(f)[1] in fileExtList] def getFileInfoClass(filename, module=sys.modules[FileInfo.__module__]): "get file info class from filename extension" subclass = "%sFileInfo" % os.path.splitext(filename)[1].upper()[1:] return hasattr(module, subclass) and getattr(module, subclass) or FileInfo return [getFileInfoClass(f)(f) for f in fileList] if __name__ == "__main__": for info in listDirectory("/music/_singles/", [".mp3"]): print "\n".join(["%s=%s" % (k, v) for k, v in info.items()]) print
下面就是从我的机器上得到的输出。你的输出将不一样,除非,由于某些令人吃惊的巧合,你与我有着共同的音乐品味。
album=
artist=Ghost in the Machine
title=A Time Long Forgotten (Concept
genre=31
name=/music/_singles/a_time_long_forgotten_con.mp3
year=1999
comment=http://mp3.com/ghostmachine
album=Rave Mix
artist=***DJ MARY-JANE***
title=HELLRAISER****Trance from Hell
genre=31
name=/music/_singles/hellraiser.mp3
year=2000
comment=http://mp3.com/DJMARYJANE
album=Rave Mix
artist=***DJ MARY-JANE***
title=KAIRO****THE BEST GOA
genre=31
name=/music/_singles/kairo.mp3
year=2000
comment=http://mp3.com/DJMARYJANE
album=Journeys
artist=Masters of Balance
title=Long Way Home
genre=31
name=/music/_singles/long_way_home1.mp3
year=2000
comment=http://mp3.com/MastersofBalan
album=
artist=The Cynic Project
title=Sidewinder
genre=18
name=/music/_singles/sidewinder.mp3
year=2000
comment=http://mp3.com/cynicproject
album=Digitosis@128k
artist=VXpanded
title=Spinning
genre=255
name=/music/_singles/spinning.mp3
year=2000
comment=http://mp3.com/artists/95/vxp
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