Python实现分割文件及合并文件的方法

#!/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, oskilobytes = 1024megabytes = kilobytes * 1000chunksize = int(1.4 * megabytes)     # default: roughly a floppydef 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 partnumif __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

#!/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, sysreadsize = 1024def 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