split.py

#!/usr/bin/env python

import  argparse

class LargeFileSplitter:
    def __init__(self, file, n):
        self.file = file
        self.num = n
        if file.endswith('.txt'):
            file = file[:-4]
        self.sub_files = [ "%s%02d.txt" % (file, i) for i in range(n) ]

    def split(self):
        with open(self.file, 'r') as f:
            lines = [ line for line in f ]
            lines_per_sub_file = len(lines) // self.num
            for i in range(self.num - 1):
                with open(self.sub_files[i], 'w') as sf:
                    sf.write(''.join(lines[i * lines_per_sub_file : (i + 1) * lines_per_sub_file]))

            with open(self.sub_files[self.num - 1], 'w') as last_sf:
                last_sf.write(''.join(lines[lines_per_sub_file * (self.num - 1) :]))


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('file', metavar='FILE', type=str, help='specify the large file to be split')
    parser.add_argument('num', metavar='N', type=int, help='specify how many sub files to split into')

    args = parser.parse_args()

    LargeFileSplitter(args.file, args.num).split()

if __name__ == '__main__':
    main()