在Python中清除终端窗口，内存/性能

Question

I'm using a script that runs for many hours, which prints statements to verify whether or not issues might have arisen (data is downloaded from the web, which sometimes gets distorted).

I've noticed a significant drop in performance after a while. I suspect that the many thousands of lines of print statements might be the reason.

It is commonly known that the terminal can be cleared of these print statements by the following line of code:

import os
os.system('cls') # for windows

Still, I suspect that this doesn't actually improve the performance speed and that it's merely a perceived improvement due to the fact that the screen is cleared. Is that true or not?

I've also considered suppressing certain print statements with the following code:

import sys
class NullWriter(object):
 def write(self, arg):
  pass
nullwrite = NullWriter()
oldstdout = sys.stdout
sys.stdout = oldstdout # enable output 
print("text that I want to see")
sys.stdout = nullwrite # disable output
print("text I don't want to see")

My question: How can I improve the performance (speed) of my script, given that I still want to see the most recent print statements?

Answer 1

If you like you can just do a line feed without a carriage return and override the last line:

sys.stdout.write("\rDoing things")
sys.stdout.flush()

Printing over time shouldn't use any extra memory within python, but you might have your terminal's buffer set to high which can use a lot of memory. Or it's just taking time to flush the buffer because you're writing so fast to stdout.

You can also use the print function

Python 2.6+

From Python 2.6 you can import the print function from Python 3:

from __future__ import print_function

This allows you to use the Python 3 solution below.

Python 3

In Python 3, the print statement has been changed into a function. In Python 3, you can instead do:

print('.', end='')