algorithm - Python: Choose random line from file, then delete that line -

i'm new python (in learned through codeacademy course) , use figuring out.

i have file, 'testingdeletelines.txt', that's 300 lines of text. right now, i'm trying print me 10 random lines file, delete lines.

so if file has 10 lines:

carrot

banana

strawberry

canteloupe

blueberry

snacks

apple

raspberry

papaya

watermelon

i need randomly pick out lines, tell me it's randomly picked blueberry, carrot, watermelon, , banana, , delete lines.

the issue is, when python reads file, reads file , once gets end, won't go , delete lines. current thinking write lines list, reopen file, match list text file, , if finds match, delete lines.

my current problem twofold:

1. it's duplicating random elements. if picks line, need not pick same line again. however, using random.sample doesn't seem work, need lines separated out when later use each line append url.

2. i don't feel logic (write array->find matches in text file->delete) ideal logic. there better way write this?

   import webbrowser import random  """url= 'http://www.google.com' webbrowser.open_new_tab(url+myline)""" eventually, need base url + 10 random lines opening in each new tab  def showmetherandoms():     x=1     deletelist= []     lines=open('testingdeletelines.txt').read().splitlines() x in range(0,10):     myline=random.choice(lines)     print(myline) """debugging, remove later"""     deletelist.append(myline)     x=x+1     print deletelist """debugging, remove later""" showmetherandoms() 

i have file, 'testingdeletelines.txt', that's 300 lines of text. right now, i'm trying print me 10 random lines file, delete lines.

#!/usr/bin/env python import random  k = 10 filename = 'testingdeletelines.txt' open(filename) file:     lines = file.read().splitlines()  if len(lines) > k:     random_lines = random.sample(lines, k)     print("\n".join(random_lines)) # print random lines      open(filename, 'w') output_file:         output_file.writelines(line + "\n"                                line in lines if line not in random_lines) elif lines: # file small     print("\n".join(lines)) # print lines     open(filename, 'wb', 0): # empty file         pass 

it o(n**2) algorithm can improved if necessary (you don't need tiny file such input)