Python 分割文件以及合并文件

#!/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