supplemental exercise for RWET

exercise.txt

(1) create a program that prints every other line of input. 
i.e., if you ran the program like so:

  $ python every_other_line.py <sea_rose.txt

it would produce the output

  Rose, harsh rose,
  meagre flower, thin,
  
  than a wet rose
  you are caught in the drift.
  Stunted, with small leaf,
  you are lifted
  that drives in the wind.
  Can the spice-rose
  hardened in a leaf?

(2) modify the program above to print every other word on 
every other line. i.e., if you ran the program like so:

  $ python every_other_line_and_word.py <sea_rose.txt

it would produce the output

  Rose, rose,
  meagre thin,
  
  than wet
  you caught the
  Stunted, small
  you lifted
  that in wind.
  Can spice-rose
  hardened a

(3) modify your program further, such that you can pass a 
number on the command line to indicate how many lines and 
words should be skipped. i.e., if you pass 3, it would 
print every third word on every third line; if you pass 4 
it would print every fourth word on every fourth line, etc. 
for example:

  $ python every_n_lines_and_words.py 3 <sea_rose.txt

would produce this output

  Rose,
  spare
  than rose
  
  you
  
  hardened leaf?

(running with "2" as the command-line parameter should 
produce exactly the same output as the program you made in 
step 2)

POTENTIALLY HELPFUL THINGS TO KNOW ABOUT (you don't have to 
use these, but they might make your task easier)

- the modulo operator, %: returns the remainder of doing 
integer division of two numbers. e.g.

  >>> 3 % 2
  1
  >>> 4 % 2
  0

- the enumerate function: 
http://www.quora.com/Asad-Awan/Learn-Python/Looping-through-a-list-using-enumerate

- the mysterious "step" parameter for list slices, 
discussed here: http://effbot.org/zone/python-list.htm 
(under the section "accessing lists")