Python

Clearing the screen of text

Please support our Python advertiser: Programming Forums - DaniWeb Sister Site

Thread Solved

•

Join Date: Jul 2008

Posts: 965

Reputation: Gribouillis is a jewel in the rough

Solved Threads: 222

Gribouillis Gribouillis is offline

Offline

Posting Shark

#11

Oct 20th, 2009

•

Originally Posted by Warkthogus

Help with Code Tags

python Syntax (Toggle Plain Text)
import os
# works on windows nt (also xp and vista) or linux
os.system(['<strong class="highlight">clear</strong>','cls'][os.name == 'nt'])
import os # works on windows nt (also xp and vista) or linux os.system(['<strong class="highlight">clear</strong>','cls'][os.name == 'nt'])
Can anyone kindly explain the background of how this bit of code works?

I suppose you pasted this from a web page. It doesn't work. The following works

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
import os
# works on windows nt (also xp and vista) or linux
os.system(['clear','cls'][os.name == 'nt'])
import os
# works on windows nt (also xp and vista) or linux
os.system(['clear','cls'][os.name == 'nt'])

if the system is nt, then os.name=='nt' returns True, which is converted to the integer 1 and ['clear','cls'][1] is 'cls', which is passed to os.system. On another system, 'clear' is passed.
This is old style coding. Nowadays, one writes

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
os.system('cls' if os.name == 'nt' else 'clear')
os.system('cls' if os.name == 'nt' else 'clear')

(By the way, using os.system is outdated too)

•

Join Date: Sep 2009

Posts: 112

Reputation: AutoPython is an unknown quantity at this point

Solved Threads: 9

AutoPython AutoPython is offline

Offline

Junior Poster

#12

Oct 20th, 2009

Well, I don't use that. I usually def them as function. Thanks for the post though anyway.

•

Join Date: Jul 2005

Posts: 1,221

Reputation: bumsfeld will become famous soon enough

Solved Threads: 138

bumsfeld

Offline

Nearly a Posting Virtuoso

#13

Oct 20th, 2009

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
import os
# works on windows nt (also xp and vista) or linux
os.system(['clear','cls'][os.name == 'nt'])
import os
# works on windows nt (also xp and vista) or linux
os.system(['clear','cls'][os.name == 'nt'])

If [os.name == 'nt'] is True then this becomes effectively 1. So it picks item at index 1 from the list which is the Windows command 'cls'. If it's False, it becomes 0 and the item at index 0 (zero) is used, which is the Linux command 'clear'.