Remove and Replace Printed items

Question

I was wondering if it was possible to remove items you have printed in Python - not from the Python GUI, but from the command prompt. e.g.

a = 0  
for x in range (0,3):  
    a = a + 1  
    b = ("Loading" + "." * a)
print (a)

so it prints

>>>Loading   
>>>Loading. 
>>>Loading.. 
>>>Loading...

But, my problem is I want this all on one line, and for it it remove it self when something else comes along. So instead of printing "Loading", "Loading.", "Loading... I want it to print "Loading.", then it removes what is on the line and replaces it with "Loading.." and then removes "Loading.." and replaces it (on the same line) with "Loading...". It's kind of hard to describe.

p.s I have tried to use the Backspace character but it doesn't seem to work ("\b")

Solution 1

Just use CR to go to beginning of the line.

import time
for x in range (0,5):  
    b = "Loading" + "." * x
    print (b, end="\r")
    time.sleep(1)

Solution 2

One way is to use ANSI escape sequences:

import sys
import time
for i in range(10):
    print("Loading" + "." * i)
    sys.stdout.write("\033[F") # Cursor up one line
    time.sleep(1)

Also sometimes useful (for example if you print something shorter than before):

sys.stdout.write("\033[K") # Clear to the end of line

Solution 3

import sys
import time

a = 0  
for x in range (0,3):  
    a = a + 1  
    b = ("Loading" + "." * a)
    # \r prints a carriage return first, so `b` is printed on top of the previous line.
    sys.stdout.write('\r'+b)
    time.sleep(0.5)
print (a)

Note that you might have to run sys.stdout.flush() right after sys.stdout.write('\r'+b) depending on which console you are doing the printing to have the results printed when requested without any buffering.

Comments

[John Howard]

Whats the point of the a variable here? You can just use x as your variable and it will do the same thing!

[Qaswed]

Two questions: 1. shouldn't be the print() command indentet to the level of the inner of the for-loop? Currently, your code doesn't print some kind of progress, but only the final state. 2. shouldn't it be print (b)? Currently only integers are printed, not the "Loading" as mentioned in the question.

[PhilMacKay]

It works in windows 7 basic terminal. In python 2.7, I simply use print "whatever to be removed\r", Thanks!

[Black Thunder]

Any idea for terminal ( IDLE )?

[Admin]

sys.stdout.write("\033[K") to clear the previous print

[markroxor]

Doesn't work in python notebooks :(

[Trevor]

Is it necessary to use sys.stdout.write() ? Can you just do print("\033[K",end='') ?

[Sven Marnach]

@Trevor This answer was written to work in both Python 2 and 3. I know the question is tagged "python-3.x", but back in 2011 hardly anyone was using Python 3, so I wrote an answer that works in both versions. If you are using Python 3, you can use print(..., end="") if you prefer.

[Dustin Michels]

@h0ussni I don't know sorcery that is but it works great

[sound wave]

sys.stdout.write('\033[2K\033[1G') erase and go to beginning of line

[DSH]

Side note: to make this work in jupyter (in python3), use: print("\r", b, end="")

[SATYAJEET RANJAN]

This works without Constant jitters in pycharm's console. The print with end ="" flickers alot in pycharm's Console

[madladzen]

Could you theoretically do sys.stdout.write("\033[F" * 2) if you wanted to cursor up 2 lines?

[Sven Marnach]

@madladzen This should work. The ANSI sequence also supports a parameter, so you could also use sys.stdout.write("\033[2F").

[do-me]

To clear all or n previously printed lines and move the cursor back to the start without flushing the entire console output every time (os.system('cls' if os.name=='nt' else 'clear') cross OS compatible) use cursor_up = '\x1b[1A';erase_line = '\x1b[2K';print("hi\nyou\nthere\nletstry!");print((cursor_up + erase_line)*4 +cursor_up);print("hi\nyou\nthere\nletstry!")

[deb]

Instead of "." * x, you should try "." * (x % 3 + 1) to avoid stuff like Loading......

[Khalil Al-rahman Yossefi]

in VS Code, and in Notebooks (ipynb), use these together: print("\r" , end="") print("delta = ", delta, end="")

[Mahrkeenerh]

I know I'm late, but my two cents: "\033[F" * 2, or "\033[2F" don't always work, as python adds the new line AFTER you go higher. So if you try to go 2 lines above and you only have one line printed, you will print the new thing on the next line, but if you have more than 1 line, the last one will be rewritten

[Sven Marnach]

@Mahrkeenerh I can't quite follow. sys.stdout.write() does not add any newline characters. print() does, which is why the code isn't using it. This answer was originally written with Python 2 in mind. In Python 3, you can also use print(..., end=""), as already mentioned in the comments above.

[Mahrkeenerh]

My mistake. I was replying to a comment, and misread the write instead of print. What I was talking about was a print("\033[F" * 2) with no end=''