Question

I have a file: test.txt with a sentence on each line.

Hello World  
99 Bottles of Beer  
Humpty Dumpty Sat on the wall

I wish to produce an output displaying all combinations of the input from this file (i.e. 2ⁿ-1 combinations). In the above instance, the algorithm will spill out the following – Each combination to be separated with a pipe (|)

Hello World  
99 Bottles of Beer  
Humpty Dumpty Sat on the wall  
Hello World | 99 Bottles of Beer  
Hello World | Humpty Dumpty Sat on the wall  
99 Bottles of Beer | Humpty Dumpty Sat on the wall  
Hello World | 99 Bottles of Beer | Humpty Dumpty Sat on the wall  

Ideally, I would like this to be done in bash or python or perl scripting but I am open to suggestions.

Answer 1

import itertools

l = [s.strip() for s in open('test.txt')]

for i in range(len(l)):
  print '\n'.join(map(' | '.join, itertools.combinations(l, i + 1)))

produces

Hello World
99 Bottles of Beer
Humpty Dumpty Sat on the wall
Hello World | 99 Bottles of Beer
Hello World | Humpty Dumpty Sat on the wall
99 Bottles of Beer | Humpty Dumpty Sat on the wall
Hello World | 99 Bottles of Beer | Humpty Dumpty Sat on the wall

If you don’t like the style of '\n'.join() (I am not sure I do), you could replace it with an explicit loop:

for i in range(len(l)):
  for c in map(' | '.join, itertools.combinations(l, i + 1)):
    print c

This is slightly more verbose, but is more economical.