Python分割文件以及合并文件

用Python进行文件操作是比较简单的，在Python中file是内置类型之一，内置的函数open、file都可以创建file对象，创建好之后就可以对其进行读写等操作。

近几天看Python Programing 3rd ，觉得书很不错。

文件分割的原理很简单：以二进制形式打开文件流，按照指定的大小读取，然后写入新文件。
文件合并的原理正好相反。

下面的代码摘自PP3rd里面。

split_file.py


#!/usr/bin/python


##########################################################################


# split a file into a set of parts; join.py puts them back together;


# this is a customizable version of the standard unix split command-line


# utility; because it is written in Python, it also works on Windows and


# can be easily modified; because it exports a function, its logic can


# also be imported and reused in other applications;


##########################################################################




import sys, os


kilobytes = 1024


megabytes = kilobytes * 1000


chunksize = int(1.4 * megabytes) # default: roughly a floppy




def split(fromfile, todir, chunksize=chunksize):


if not os.path.exists(todir): # caller handles errors


os.mkdir(todir) # make dir, read/write parts


else:


for fname in os.listdir(todir): # delete any existing files


os.remove(os.path.join(todir, fname))


partnum = 0


input = open(fromfile, 'rb') # use binary mode on Windows


while 1: # eof=empty string from read


chunk = input.read(chunksize) # get next part <= chunksize


if not chunk: break


partnum = partnum+1


filename = os.path.join(todir, ('part%04d' % partnum))


fileobj = open(filename, 'wb')


fileobj.write(chunk)


fileobj.close() # or simply open().write()


input.close()


assert partnum <= 9999 # join sort fails if 5 digits


return partnum




if __name__ == '__main__':


if len(sys.argv) == 2 and sys.argv[1] == '-help':


print 'Use: split.py [file-to-split target-dir [chunksize]]'


else:


if len(sys.argv) < 3:


interactive = 1


fromfile = raw_input('File to be split? ') # input if clicked


todir = raw_input('Directory to store part files? ')


else:


interactive = 0


fromfile, todir = sys.argv[1:3] # args in cmdline


if len(sys.argv) == 4: chunksize = int(sys.argv[3])


absfrom, absto = map(os.path.abspath, [fromfile, todir])


print 'Splitting', absfrom, 'to', absto, 'by', chunksize




try:


parts = split(fromfile, todir, chunksize)


except:


print 'Error during split:'


print sys.exc_info()[0], sys.exc_info()[1]


else:


print 'Split finished:', parts, 'parts are in', absto


if interactive: raw_input('Press Enter key') # pause if clicked

join_file.py


#!/usr/bin/python


##########################################################################


# join all part files in a dir created by split.py, to recreate file.


# This is roughly like a 'cat fromdir/* > tofile' command on unix, but is


# more portable and configurable, and exports the join operation as a


# reusable function. Relies on sort order of file names: must be same


# length. Could extend split/join to popup Tkinter file selectors.


##########################################################################




import os, sys


readsize = 1024




def join(fromdir, tofile):


output = open(tofile, 'wb')


parts = os.listdir(fromdir)


parts.sort()


for filename in parts:


filepath = os.path.join(fromdir, filename)


fileobj = open(filepath, 'rb')


while 1:


filebytes = fileobj.read(readsize)


if not filebytes: break


output.write(filebytes)


fileobj.close()


output.close()




if __name__ == '__main__':


if len(sys.argv) == 2 and sys.argv[1] == '-help':


print 'Use: join.py [from-dir-name to-file-name]'


else:


if len(sys.argv) != 3:


interactive = 1


fromdir = raw_input('Directory containing part files? ')


tofile = raw_input('Name of file to be recreated? ')


else:


interactive = 0


fromdir, tofile = sys.argv[1:]


absfrom, absto = map(os.path.abspath, [fromdir, tofile])


print 'Joining', absfrom, 'to make', absto




try:


join(fromdir, tofile)


except:


print 'Error joining files:'


print sys.exc_info()[0], sys.exc_info()[1]


else:


print 'Join complete: see', absto


if interactive: raw_input('Press Enter key') # pause if clicked



以上代码在window下面测试成功，可以分割文件文件已经任何二进制文件。