Question

I am using following code to pickup 10 random lines, however it’s also pickups empty line. I just wanted to exclude empty line while doing selection. and also wants to mark selected line with * as prefix. so next time this code will not pickup any line which start with *.

import random  
task = 10  
while ( task >= 0 ):  
    lines = open('master.txt').read().splitlines()
    myline =random.choice(lines)    
    print(myline)  
    task -= 1  
print ('Done!')

Answer 1

The following will randomly select 10 lines that are non-empty and not marked. The selected lines are printed out and the file is updated such that the selected lines are marked (prepended with *) and empty lines removed.

import random
num_lines = 10

# read the contents of your file into a list
with open('master.txt', 'r') as f:
  lines = [L for L in f if L.strip()]  # store non-empty lines

# get the line numbers of lines that are not marked
candidates = [i for i, L in enumerate(lines) if not L.startswith("*")] 

# if there are too few candidates, simply select all
if len(candidates) > num_lines:
  selected = random.sample(candidates, num_lines) 
else:
  selected = candidates  # choose all

# print the lines that were selected
print "".join(lines[i] for i in selected)

# Mark selected lines in original content
for i in selected:
  lines[i] = "*%s" % lines[i]  # prepend "*" to selected lines

# overwrite the file with modified content
with open('master.txt', 'w') as f:
  f.write("".join(lines))