Python: How to print on same line, clearing previous text?

Question

In Python you can print on the same line using \r to move back to the start of the line.

This works well for progress bars or increasing precentage counters, eg: Python print on same line

However when printing lines that may decrease in length, this leaves the previous lines text there, eg:

import sys
for t in ['long line', '%']:
    sys.stdout.write(t + '\r')
sys.stdout.write('\n')

Leaves the terminal text as: %ong line.

Whats the best way to write a shorter line after a longer one, when printing to the same line?

Note that some of the answers to https://stackoverflow.com/questions/3249524 (lower down on the page), cover this question, but the question is in fact different. — ideasman42, Jul 23 '17 at 09:39
Does this answer your question? [How to overwrite the previous print to stdout?](https://stackoverflow.com/questions/5419389/how-to-overwrite-the-previous-print-to-stdout) — Karl Knechtel, Jan 02 '23 at 00:16
@karl-knechtel that question doesn't ask about the problem of trailing text being left when using `\r`. — ideasman42, Jan 03 '23 at 00:44
It doesn't ask explicitly, perhaps because it didn't occur to OP as a problem; but it's a common inference, and is addressed by the top answer there. — Karl Knechtel, Jan 03 '23 at 00:47

ideasman42 · Accepted Answer · 2020-12-07T22:27:42.130

10

Along with \r, the ansi-sequence \033[K is needed - erase to end of line.

This code works as expected.

import sys
for t in ['long line', '%']:
    sys.stdout.write('\033[K' + t + '\r')
sys.stdout.write('\n')

Note, this doesn't work when the string includes tabs, you may want to replace:

sys.stdout.write('\033[K' + t + '\r') with ...

sys.stdout.write('\033[K' + t.expandtabs(2) + '\r')

edited Dec 07 '20 at 22:27

answered Jul 23 '17 at 09:43

ideasman42

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I found that the erase sequence interferes with space-expanded tabs unless you put it in a separate string like `print('\033[K' + '\tWords here'.expandtabs(2))` – Addison Klinke Dec 07 '20 at 19:51
Thanks for pointing this out, added note, I'm not sure if there is a better way to solve this than what you've suggested. – ideasman42 Dec 07 '20 at 22:28
Can you explain why you added the `\r` to the end of the string? I tried it with `print('\r\033[K'+t)` and it seems to work. – Manngo Apr 05 '22 at 23:56
It can be at the beginning of the line too, the cursor will then be left at the end. – ideasman42 Apr 06 '22 at 02:17

score 2 · Answer 2 · answered Mar 17 '22 at 05:40

If you have been printing without a newline character at the end of your print, you can flush your latest print with:

print('\r\033[K', end='')

If you previously printed with a new line, you can use the ANSI escape code to move up one line and to the beginning of the line with:

print('\033[F', end='')

You can then flush the line as before.

An example usage:

LINE_FLUSH = '\r\033[K'
UP_FRONT_LINE = '\033[F'
...
print(UP_FRONT_LINE + LINE_FLUSH + msg)

score 1 · Answer 3 · answered Jul 23 '17 at 09:26

I think the simplest way to do this is to write spaces over the characters. For this, it'd be a good idea to write as many spaces are needed to cover the last line only. Example:

previousLength = 0
for t in ["long line", "%"]:
    print(" " * previousLength, end="\r") 
    print(t, end="\r")

    previousLength = len(t)

print("\n")

Python: How to print on same line, clearing previous text?

3 Answers3

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