Try this: os.system("cls")
os.system('clear') works on linux. If you are running windows try os.system('CLS') instead.
You need to import os first like this:
import os
The way to execute commands in Python 2.4+ is to use the subprocess module. You can use it in the same way that you use os.system.
import subprocess
subprocess.call("clear") # linux/mac
subprocess.call("cls", shell=True) # windows
If you're executing this in the python console, you'll need to do something to hide the return value (for either os.system or subprocess.call), like assigning it to a variable:
cls = subprocess.call("cls", shell=True)
The "cls" and "clear" are commands which will clear a terminal (ie a DOS prompt, or terminal window). From your screenshot, you are using the shell within IDLE, which won't be affected by such things. Unfortunately, I don't think there is a way to clear the screen in IDLE. The best you could do is to scroll the screen down lots of lines, eg:
print "\n" * 100
Though you could put this in a function:
def cls(): print "\n" * 100
And then call it when needed as cls()
Your screenshot shows you're using IDLE. cls/clear won't work for you.
As mark.ribau said, it seems that there is no way to clear the Text widget in idle. One should edit the EditorWindow.py module and add a method and a menu item in the EditorWindow class that does something like:
self.text.tag_remove("sel", "1.0", "end")
self.text.delete("1.0", "end")
and perhaps some more tag management of which I'm unaware of.