Handling multiline carriage returns

Question

So, there's this problem that I have.

When you have a a \r string, you can update the printed line:

print('\r' + "Some string", end='')
print('\r' + "Updated string", end='')

However, if a string is too long, it'll get truncated to a new console line, which will force a newline, thus breaking the "seamless" string update.

Is there a way to prevent this?

You could print something like `'\r' + SomeString[:79]`, to truncate it rather than wrapping (assuming an 80-character wide window). If you *must* print the whole thing, yet still be able to overwrite the entire value, you are in the territory of the `curses` module. — jasonharper, Oct 05 '21 at 16:32
You're probably looking for the `textwrap` library https://docs.python.org/3/library/textwrap.html — ti7, Oct 05 '21 at 17:11

ti7 · Answer 1 · 2021-10-06T16:03:03.600

You're probably much better off buffering all the messages you want together and using a textwrap.wrap to present them!

You may be able to collect more easily via contextlib.redirect_stdout see this answer to Capture stdout from a script?

If you have many threads or processes, collecting the outputs into some queue for display by a single one is a practical approach

Example Use

import io
import textwrap
from contextlib import redirect_stdout

buffer = io.StringIO()

with redirect_stdout(buffer):
    # print() calls in this context will go to the buffer instead of stdout
    # put whatever logic you were print()-ing from here
    # likely one or several function calls
    print("a very long string example" * 10)
    print("1111111" * 20)
    print("some\n new\r\nlines\n")
    print("a string example with space " * 10)

# get one big string, replacing newlines with spaces
buffered_content = buffer.getvalue().replace("\n", " ")

# use a textwrap method to display the output, setting any options needed
# textwrap returns a list of lines, so they can be joined or printed individually
print("\n".join(textwrap.wrap(buffered_content)))

Output

% python3 test.py
a very long string examplea very long string examplea very long string
examplea very long string examplea very long string examplea very long
string examplea very long string examplea very long string examplea
very long string examplea very long string example 1111111111111111111
1111111111111111111111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111 some  new  lines
a string example with space a string example with space a string
example with space a string example with space a string example with
space a string example with space a string example with space a string
example with space a string example with space a string example with
space

If you want to continually display at some interval or quantity of content, you can keep the the last value of the textwrap (beware: it may be an empty list if no input is provided).. as the input to a later .wrap() to keep the line wrapping going until the end of your process

Handling multiline carriage returns

1 Answers1

Example Use

Output