# 5.1. 概览 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 string`s](../getting_to_know_python/documenting_functions.html "2.3. 文档化函数")，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。 ## 例 5.1. `fileinfo.py` 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](http://www.woodpecker.org.cn/diveintopython/download/diveintopython-exampleszh-cn-5.4b.zip "Download example scripts")。 ``` """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 ``` | | | | --- | --- | | \[1\] | 这个程序的输入要取决于你硬盘上的文件。为了得到有意义的输出，你应该修改目录路径指向你自已机器上的一个 MP3 文件目录。 | 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 ```