python 文件分割

import sys,os

def split(fromfile,todir,chunksize):

    partnum =
    inputfile = open(fromfile,'rb')#open the fromfile
    while True:
        chunk = inputfile.read(chunksize)
        if not chunk:             #check the chunk is empty
            break
        partnum +=
        filename = os.path.join(todir,('{0}{1}.4'.format("jj",partnum)))
        fileobj = open(filename,'wb')#make partfile
        fileobj.write(chunk)         #write data into partfile
        fileobj.close()
    return partnum

chunksize = *(**)
fromfile  = input('File to be split?')
todir = input('Directory to store part files?')
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()[],sys.exc_info()[])
else:
    print('split finished:',parts,'parts are in',absto)