Read file N lines at a time

read_n.py

import string
from itertools import islice


def next_n_lines(file_opened, N, strip='right'):
    '''
    Each call of this function returns next N lines of fileopen.
    Usage:
    strip='right' -> remove trailing whitespace characters in each line,
    strip='left' -> remove leading whitespace characters in each line,
    strip='both' -> remove both trailing and leading whitespace characters in each line,
    strip=None -> do not remove any characters.
  
    Note: CANNOT be used together with readline() or readlines() method.
    '''
    strip_dic = {
      'right': string.rstrip,
      'left': string.lstrip,
      'both': string.strip
    }
    if strip:
        return [strip_dic[strip](x) for x in islice(file_opened, N)]
    else:
        return list(islice(file_opened, N))