最基本的文件操做固然就是在文件中读写数据。这也是很容易掌握的。如今打开一个文件以进行写操做:
1. fileHandle = open ( 'test.txt', 'w' )
fileHandle = open ( 'test.txt', 'w' )
‘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:
1. fileHandle.write ( 'This is a test.\nReally, it is.' )
fileHandle.write ( 'This is a test.\nReally, it is.' )
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,咱们须要作清理工做,而且关闭文件:
1. fileHandle.close()
fileHandle.close()
正如你所见,在Python的面向对象机制下,这确实很是简单。须要注意的是,当你再次使用“w”方式在文件中写数据,全部原来的内容都会被删除。若是想保留原来的内容,可使用“a”方式在文件中结尾附加数据:
1. fileHandle = open ( 'test.txt', 'a' )
2. fileHandle.write ( '\n\nBottom line.' )
3. fileHandle.close()
fileHandle = open ( 'test.txt', 'a' )
fileHandle.write ( '\n\nBottom line.' )
fileHandle.close()
而后,咱们读取test.txt,并将内容显示出来:
1. fileHandle = open ( 'test.txt' )
2. print fileHandle.read()
3. fileHandle.close()
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。咱们也能够读取文件中的一行:
1. fileHandle = open ( 'test.txt' )
2. print fileHandle.readline() # "This is a test."
3. fileHandle.close()
fileHandle = open ( 'test.txt' )
print fileHandle.readline() # "This is a test."
fileHandle.close()
同时,也能够将文件内容保存到一个list中:
1. fileHandle = open ( 'test.txt' )
2. fileList = fileHandle.readlines()<div></div>
3. for fileLine in fileList:
4. print '>>', fileLine
5. fileHandle.close()
fileHandle = open ( 'test.txt' )
fileList = fileHandle.readlines()
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,以下所示:
1. fileHandle = open ( 'test.txt' )
2. garbage = fileHandle.readline()
3. fileHandle.readline() # "Really, it is."fileHandle.close()
fileHandle = open ( 'test.txt' )
garbage = fileHandle.readline()
fileHandle.readline() # "Really, it is."fileHandle.close()
能够看到,只有第二行显示出来。然而,咱们可让Python从头开始读来解决这个问题:
1. fileHandle = open ( 'test.txt' )
2. garbage = fileHandle.readline()
3. fileHandle.seek ( 0 )
4. print fileHandle.readline() # "This is a test."
5. fileHandle.close()
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,咱们让Python从文件第一个字节开始读取数据。因此,第一行文字显示了出来。固然,咱们也能够获取Python在文件中的位置:
1. fileHandle = open ( 'test.txt' )
2. print fileHandle.readline() # "This is a test."
3. print fileHandle.tell() # "17"
4. print fileHandle.readline() # "Really, it is."
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:
1. fileHandle = open ( 'test.txt' )
2. print fileHandle.read ( 1 ) # "T"
3. fileHandle.seek ( 4 )
4. print FileHandle.read ( 1 ) # " "(原文有错)
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,有时可能须要以二进制方式读写文件,好比图片和可执行文件。此时,只要在打开文件的方式参数中增长一个“b”便可:
1. fileHandle = open ( 'testBinary.txt', 'wb' )
2. fileHandle.write ( 'There is no spoon.' )
3. fileHandle.close()
fileHandle = open ( 'testBinary.txt', 'wb' )
fileHandle.write ( 'There is no spoon.' )
fileHandle.close()
1. fileHandle = open ( 'testBinary.txt', 'rb' )
2. print fileHandle.read()
3. fileHandle.close()
fileHandle = open ( 'testBinary.txt', 'rb' )
print fileHandle.read()
fileHandle.close()
2、从现有文件中获取信息
使用Python中的模块,能够从现有文件中获取信息。使用“os”模块和“stat”模块能够获取文件的基本信息:
1. import os
2. import stat
3. import time<div></div>
4.
5. fileStats = os.stat ( 'test.txt' )
6. fileInfo = {
7. 'Size' : fileStats [ stat.ST_SIZE ],
8. 'LastModified' : time.ctime ( fileStats [ stat.ST_MTIME ] ),
9. 'LastAccessed' : time.ctime ( fileStats [ stat.ST_ATIME ] ),
10. 'CreationTime' : time.ctime ( fileStats [ stat.ST_CTIME ] ),
11. 'Mode' : fileStats [ stat.ST_MODE ]
12. }
13.
14. for infoField, infoValue in fileInfo:
15. print infoField, ':' + infoValue
16. if stat.S_ISDIR ( fileStats [ stat.ST_MODE ] ):
17. print 'Directory. '
18. else:
19. print 'Non-directory.'
import os
import stat
import time
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.'
上面这个例子建立了一个包含文件基本信息的dictionary。而后显示了相关信息,而且告诉咱们打开的是否为目录。咱们也能够试一下打开的是不是其它几种类型:
1. import os
2. import stat
3.
4. fileStats = os.stat ( 'test.txt' )
5. fileMode = fileStats [ stat.ST_MODE ]
6. if stat.S_ISREG ( fileStats [ stat.ST_MODE ] ):
7. print 'Regular file.'
8. elif stat.S_ISDIR ( fileStats [ stat.ST_MODE ] ):
9. print 'Directory.'
10. elif stat.S_ISLNK ( fileStats [ stat.ST_MODE ] ):
11. print 'Shortcut.'
12. elif stat.S_ISSOCK ( fileStats [ stat.ST_MODE ] ):
13. print 'Socket.'
14. elif stat.S_ISFIFO ( fileStats [ stat.ST_MODE ] ):
15. print 'Named pipe.'
16. elif stat.S_ISBLK ( fileStats [ stat.ST_MODE ] ):
17. print 'Block special device.'
18. elif stat.S_ISCHR ( fileStats [ stat.ST_MODE ] ):
19. print 'Character special device.'
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 ] ):
print 'Character special device.'
另外,咱们可使用“os.path”来获取基本信息:
1. import os.path
2.
3. fileStats = 'test.txt'
4. if os.path.isdir ( fileStats ):
5. print 'Directory.'
6. elif os.path.isfile ( fileStats ):
7. print 'File.'
8. elif os.path.islink ( fileStats ):
9. print 'Shortcut.'
10. elif os.path.ismount ( fileStats ):
11. print 'Mount point.'
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.'
3、目录
和普通文件同样,关于目录的操做也很容易掌握。首先,列出一个目录的内容:
1. import os
2.
3. for fileName in os.listdir ( '/' ):
4. print fileName
import os
for fileName in os.listdir ( '/' ):
print fileName
正如你所见,这很简单,用三行代码就能够完成。
建立目录也很简单:
1. import os
2.
3. os.mkdir ( 'testDirectory' )
import os
os.mkdir ( 'testDirectory' )
删除刚才建立的目录:
1. import os
2.
3. os.rmdir ( 'testDirectory )
import os
os.rmdir ( 'testDirectory )
嗯,能够建立多级目录:
1. import os
2.
3. os.makedirs ( 'I/will/show/you/how/deep/the/rabbit/hole/goes' )
import os
os.makedirs ( 'I/will/show/you/how/deep/the/rabbit/hole/goes' )
若是没有在建立的文件夹中添加任何东西,就能够一次性将它们所有删除(即,删除所列的全部空文件夹):
1. import os
2.
3. os.removedirs ( 'I/will/show/you/how/deep/the/rabbit/hole/goes' )
import os
os.removedirs ( 'I/will/show/you/how/deep/the/rabbit/hole/goes' )
当须要对一个特定的文件类型进行操做时,咱们能够选择“fnmatch”模块。如下是显示“.txt”文件的内容和“.exe”文件的文件名:
1. import fnmatch
2. import os
3.
4. for fileName in os.listdir ( '/' ):
5. if fnmatch.fnmath ( fileName, '*.txt' ):
6. print open ( fileName ).read()
7. elif fnmatch.fnmatch ( fileName, '*.exe' ):
8. print fileName
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
“*”字符能够表示任意长度的字符。若是要匹配一个字符,则使用“?”符号:
1. import fnmatch
2. import os
3.
4. for fileName in os.listdir ( '/' ):
5. if fnmatch.fnmatch ( fileName, '?.txt' ):
6. print 'Text file.'
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:
1. import fnmatch
2. import os
3. import re
4.
5. filePattern = fnmatch.translate ( '*.txt' )
6. for fileName in os.listdir ( '/' ):
7. if re.match ( filePattern, fileName ):
8. print 'Text file.'
import fnmatch
import os
import re
filePattern = fnmatch.translate ( '*.txt' )
for fileName in os.listdir ( '/' ):
if re.match ( filePattern, fileName ):
print 'Text file.'
若只须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”类似:
1. import glob
2.
3. for fileName in glob.glob ( '*.txt' ):
4. print 'Text file.'
import glob
for fileName in glob.glob ( '*.txt' ):
print 'Text file.'
使用必定范围的字符来匹配一样可行,就像在正则表达式中使用同样。假设你想要显示扩展名前只有一位数字的文件的文件名:
1. import glob
2.
3. for fileName in glob.glob ( '[0-9].txt' ):
4. print filename
import glob
for fileName in glob.glob ( '[0-9].txt' ):
print filename
“glob”模块利用“fnmatch”模块来实现。
4、数据编组
使用前一节中介绍的模块,能够实如今文件中对字符串的读写。
然而,有的时候,你可能须要传递其它类型的数据,如list、tuple、dictionary和其它对象。在Python中,你可使用Pickling来完成。你可使用Python标准库中的“pickle”模块完成数据编组。
下面,咱们来编组一个包含字符串和数字的list:
1. import pickle
2.
3. fileHandle = open ( 'pickleFile.txt', 'w' )
4. testList = [ 'This', 2, 'is', 1, 'a', 0, 'test.' ]
5. pickle.dump ( testList, fileHandle )
6. fileHandle.close()
import pickle
fileHandle = open ( 'pickleFile.txt', 'w' )
testList = [ 'This', 2, 'is', 1, 'a', 0, 'test.' ]
pickle.dump ( testList, fileHandle )
fileHandle.close()
拆分编组一样不难:
1. import pickle
2.
3. fileHandle = open ( 'pickleFile.txt' )
4. testList = pickle.load ( fileHandle )
5. fileHandle.close()
import pickle
fileHandle = open ( 'pickleFile.txt' )
testList = pickle.load ( fileHandle )
fileHandle.close()
如今试试存储更加复杂的数据:
1. import pickle
2.
3. fileHandle = open ( 'pickleFile.txt', 'w' )
4. testList = [ 123, { 'Calories' : 190 }, 'Mr. Anderson', [ 1, 2, 7 ] ]
5. pickle.dump ( testList, fileHandle )
6. fileHandle.close()
import pickle
fileHandle = open ( 'pickleFile.txt', 'w' )
testList = [ 123, { 'Calories' : 190 }, 'Mr. Anderson', [ 1, 2, 7 ] ]
pickle.dump ( testList, fileHandle )
fileHandle.close()
1. import pickle
2.
3. fileHandle = open ( 'pickleFile.txt' )
4. testList = pickle.load ( fileHandle )
5. 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。众多对象能够经过它来存储到文件中。若是能够的话,“cPickle”一样胜任这个工做。它和“pickle”模块同样,可是速度更快:
1. import cPickle
2.
3. fileHandle = open ( 'pickleFile.txt', 'w' )
4. cPickle.dump ( 1776, fileHandle )
5. fileHandle.close()
import cPickle
fileHandle = open ( 'pickleFile.txt', 'w' )
cPickle.dump ( 1776, fileHandle )
fileHandle.close()
5、建立“虚拟”文件
你用到的许多模块包含须要文件对象做为参数的方法。可是,有时建立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,你可使用“StringIO”模块来建立文件并将其保存在内存中:
1. import StringIO
2.
3. fileHandle = StringIO.StringIO ( "Let freedom ring" )
4. print fileHandle.read() # "Let freedom ring."
5. fileHandle.close()
import StringIO
fileHandle = StringIO.StringIO ( "Let freedom ring" )
print fileHandle.read() # "Let freedom ring."
fileHandle.close()
cStringIO”模块一样有效。它的使用方法和“StringIO”同样,但就像“cPickle”之于“pickle”,它速度更快:
1. import cStringIO
2.
3. fileHandle = cStringIO.cStringIO ( "To Kill a Mockingbird" )
4. print fileHandle.read() # "To Kill a Mockingbid"
5. fileHandle.close()
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常常遇到的问题。幸亏,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做。
好了,如今你已经了解了Python中文件管理的基本知识,能够在从此的应用程序中很好地使用了。
程序员