Python 文件管理实例详解
本文实例讲述了Python 文件管理的方法。分享给大家供大家参考，具体如下：
一、Python中的文件管理
文件管理是很多应用程序的基本功能和重要组成部分。Python可以使文件管理极其简单，特别是和其它语言相对比。
以下，Peyton McCullough讲解了文件管理基础。
介绍
你玩过的游戏使用文件来保存存档；你下的订单保存在文件中；很明显，你早上写的报告也保存在文件中。
几乎以任何语言编写的众多应用程序中，文件管理是很重要的一部分。Python当然也不例外。在这篇文章中，我们将探究如何使用一些模块来操作文件。我们会完成读文件，写文件，增加文件内容的操作，还有一些另类的用法。OK，让我们开始吧。
读写文件
最基本的文件操作当然就是在文件中读写数据。这也是很容易掌握的。现在打开一个文件以进行写操作：
'w'是指文件将被写入数据，语句的其它部分很好理解。下一步就是将数据写入文件：
这个语句将"This is a test."写入文件的第一行，"Really, it is."写入文件的第二行。最后，我们需要做清理工作，并且关闭文件：
正如你所见，在Python的面向对象机制下，这确实非常简单。需要注意的是，当你再次使用"w"方式在文件中写数据，所有原来的内容都会被删除。如果想保留原来的内容，可以使用"a"方式在文件中结尾附加数据：
fileHandle = open ( 'test.txt', 'a' ) fileHandle.write ( '\n\nBottom line.' ) fileHandle.close()
然后，我们读取test.txt，并将内容显示出来：
fileHandle = open ( 'test.txt' ) print fileHandle.read() fileHandle.close()
以上语句将读取整个文件并显示其中的数据。我们也可以读取文件中的一行：
fileHandle = open ( 'test.txt' ) print fileHandle.readline() # "This is a test." fileHandle.close()
同时，也可以将文件内容保存到一个list中：
fileHandle = open ( 'test.txt' ) fileList = fileHandle.readlines()<DIV></DIV> for fileLine in fileList: print '>>', fileLine fileHandle.close()
Python在读取一个文件时，会记住其在文件中的位置，如下所示：
fileHandle = open ( 'test.txt' ) garbage = fileHandle.readline() fileHandle.readline() # "Really, it is."fileHandle.close()
可以看到，只有第二行显示出来。然而，我们可以让Python从头开始读来解决这个问题：
fileHandle = open ( 'test.txt' ) garbage = fileHandle.readline() fileHandle.seek ( 0 ) print fileHandle.readline() # "This is a test." fileHandle.close()
在上面这个例子中，我们让Python从文件第一个字节开始读取数据。所以，第一行文字显示了出来。当然，我们也可以获取Python在文件中的位置：
fileHandle = open ( 'test.txt' ) print fileHandle.readline() # "This is a test." print fileHandle.tell() # "17" print fileHandle.readline() # "Really, it is."
或者在文件中一次读取几个字节的内容：
fileHandle = open ( 'test.txt' ) print fileHandle.read ( 1 ) # "T" fileHandle.seek ( 4 ) print FileHandle.read ( 1 ) # " "(原文有错)
在Windows和Macintosh环境下，有时可能需要以二进制方式读写文件，比如图片和可执行文件。此时，只要在打开文件的方式参数中增加一个"b"即可：
fileHandle = open ( 'testBinary.txt', 'wb' ) fileHandle.write ( 'There is no spoon.' ) fileHandle.close() fileHandle = open ( 'testBinary.txt', 'rb' ) print fileHandle.read() fileHandle.close()
二、从现有文件中获取信息
使用Python中的模块，可以从现有文件中获取信息。使用"os"模块和"stat"模块可以获取文件的基本信息：
import os
import stat
import time<DIV></DIV>
fileStats = os.stat ( 'test.txt' )
fileInfo = {
'Size' : fileStats [ stat.ST_SIZE ],
'LastModified' : time.ctime ( fileStats [ stat.ST_MTIME ] ),
'LastAccessed' : time.ctime ( fileStats [ stat.ST_ATIME ] ),
'CreationTime' : time.ctime ( fileStats [ stat.ST_CTIME ] ),
'Mode' : fileStats [ stat.ST_MODE ]
}
for infoField, infoValue in fileInfo:
print infoField, ':' + infoValue
if stat.S_ISDIR ( fileStats [ stat.ST_MODE ] ):
print 'Directory. '
else:
print 'Non-directory.'
上面这个例子创建了一个包含文件基本信息的dictionary。然后显示了相关信息，并且告诉我们打开的是否为目录。我们也可以试一下打开的是否是其它几种类型：
import os import stat fileStats = os.stat ( 'test.txt' ) fileMode = fileStats [ stat.ST_MODE ] if stat.S_ISREG ( fileStats [ stat.ST_MODE ] ): print 'Regular file.' elif stat.S_ISDIR ( fileStats [ stat.ST_MODE ] ): print 'Directory.' elif stat.S_ISLNK ( fileStats [ stat.ST_MODE ] ): print 'Shortcut.' elif stat.S_ISSOCK ( fileStats [ stat.ST_MODE ] ): print 'Socket.' elif stat.S_ISFIFO ( fileStats [ stat.ST_MODE ] ): print 'Named pipe.' elif stat.S_ISBLK ( fileStats [ stat.ST_MODE ] ): print 'Block special device.' elif stat.S_ISCHR ( fileStats [ stat.ST_MODE ] ):
另外，我们可以使用"os.path"来获取基本信息：
import os.path fileStats = 'test.txt' if os.path.isdir ( fileStats ): print 'Directory.' elif os.path.isfile ( fileStats ): print 'File.' elif os.path.islink ( fileStats ): print 'Shortcut.' elif os.path.ismount ( fileStats ): print 'Mount point.' import os for fileName in os.listdir ( '/' ): print fileName
正如你所见，这很简单，用三行代码就可以完成。
创建目录也很简单：
import os os.mkdir ( 'testDirectory' )
删除刚才创建的目录：
import os os.rmdir ( 'testDirectory )
也可以创建多级目录：
import os
os.makedirs ( 'I/will/show/you/how/deep/the/rabbit/hole/goes' )
os.makedirs ( 'I/will/show/you/how/deep/the/rabbit/hole/goes' )
如果没有在创建的文件夹中添加任何东西，就可以一次性将它们全部删除（即，删除所列的所有空文件夹）：
import os os.removedirs ( 'I/will/show/you/how/deep/the/rabbit/hole/goes'
当需要对一个特定的文件类型进行操作时，我们可以选择"fnmatch"模块。以下是显示".txt"文件的内容和".exe"文件的文件名：
import fnmatch
import os
for fileName in os.listdir ( '/' ):
if fnmatch.fnmath ( fileName, '*.txt' ):
print open ( fileName ).read()
elif fnmatch.fnmatch ( fileName, '*.exe' ):
print fileName
字符可以表示任意长度的字符。如果要匹配一个字符，则使用"?"符号：
import fnmatch
import os
for fileName in os.listdir ( '/' ):
if fnmatch.fnmatch ( fileName, '?.txt' ):
print 'Text file.'
"fnmatch"模块支持正则表达式：
import fnmatch
import os
import re
filePattern = fnmatch.translate ( '*.txt' )
for fileName in os.listdir ( '/' ):
if re.match ( filePattern, fileName ):
print 'Text file.'
若只需要匹配一种类型的文件，更好的办法是使用"glob"模块。该模块的格式和"fnmatch"相似：
import glob for fileName in glob.glob ( '*.txt' ): print 'Text file.'
使用一定范围的字符来匹配同样可行，就像在正则表达式中使用一样。假设你想要显示扩展名前只有一位数字的文件的文件名：
import glob for fileName in glob.glob ( '[0-9].txt' ): print filename
"glob"模块利用"fnmatch"模块来实现。
四、数据编组
使用前一节中介绍的模块，可以实现在文件中对字符串的读写。
然而，有的时候，你可能需要传递其它类型的数据，如list、tuple、dictionary和其它对象。在Python中，你可以使用Pickling来完成。你可以使用Python标准库中的"pickle"模块完成数据编组。
下面，我们来编组一个包含字符串和数字的list：
import pickle fileHandle = open ( 'pickleFile.txt', 'w' ) testList = [ 'This', 2, 'is', 1, 'a', 0, 'test.' ] pickle.dump ( testList, fileHandle ) fileHandle.close()
拆分编组同样不难：
import pickle fileHandle = open ( 'pickleFile.txt' ) testList = pickle.load ( fileHandle ) fileHandle.close()
现在试试存储更加复杂的数据：
import pickle
fileHandle = open ( 'pickleFile.txt', 'w' )
testList = [ 123, { 'Calories' : 190 }, 'Mr. Anderson', [ 1, 2, 7 ] ]
pickle.dump ( testList, fileHandle )
fileHandle.close()
import pickle
fileHandle = open ( 'pickleFile.txt' )
testList = pickle.load ( fileHandle )
fileHandle.close()
如上所述，使用Python的"pickle"模块编组确实很简单。众多对象可以通过它来存储到文件中。如果可以的话，"cPickle"同样胜任这个工作。它和"pickle"模块一样，但是速度更快：
import cPickle fileHandle = open ( 'pickleFile.txt', 'w' ) cPickle.dump ( 1776, fileHandle ) fileHandle.close()
五、创建"虚拟"文件
你用到的许多模块包含需要文件对象作为参数的方法。但是，有时创建并使用一个真实的文件并让人感到有些麻烦。所幸的是，在Python中，你可以使用"StringIO"模块来创建文件并将其保存在内存中：
import StringIO fileHandle = StringIO.StringIO ( "Let freedom ring" ) print fileHandle.read() # "Let freedom ring." fileHandle.close()
cStringIO"模块同样有效。它的使用方法和"StringIO"一样，但就像"cPickle"之于"pickle"，它速度更快：
import cStringIO fileHandle = cStringIO.cStringIO ( "To Kill a Mockingbird" ) print fileHandle.read() # "To Kill a Mockingbid" fileHandle.close()
结论
文件管理，是众多编程语言的程序员在编写应用程序是经常遇到的问题。幸好，和其它语言相比，Python使其出乎意料地容易。Python的标准库中提供了许多相关的模块帮助程序员解决这方面的问题，而它的面向对象的机制也简化了操作。
好了，现在你已经了解了Python中文件管理的基本知识，可以在今后的应用程序中很好地使用了。
希望本文所述对大家Python程序设计有所帮助。
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