Python not finding carriage returns (^M or \r) visible to nano and vi

Question

I am currently writing a bash script that returns the output of the functions it performs as a log file. When this is viewed in Notepad text showing the process of a function takes up the bulk of the file. Ideally I don't want all this bulk and I just want to show the last output piece of progress text showing the process has been performed successfully.

output_log_18_01_2024.log - Notepad
+---------------------------------------------------------------------------+
 Reading flash ............... 0x00000000 (0%) 
 Reading flash ............... 0x00001000 (0%) 
 Reading flash ............... 0x00002000 (0%) 
 Reading flash ............... 0x00003000 (0%) 
 Reading flash ............... 0x00004000 (0%) 
 Reading flash ............... 0x00005000 (0%) 
 Reading flash ............... 0x00006000 (0%) 
 Reading flash ............... 0x00007000 (0%) 
 Reading flash ............... 0x00008000 (0%) 
 Reading flash ............... 0x00009000 (0%) 
 Reading flash ............... 0x0000A000 (0%) 
 Reading flash ............... 0x0000B000 (0%) 
 Reading flash ............... 0x0000C000 (0%) 
 Reading flash ............... 0x0000D000 (0%) 
 Reading flash ............... 0x0000E000 (0%) 
 Reading flash ............... 0x0000F000 (0%) 
 Reading flash ............... 0x00010000 (0%) 
 Reading flash ............... 0x00011000 (0%) 
 Reading flash ............... 0x00012000 (0%) 
 Reading flash ............... 0x00013000 (0%)
 ...

When viewed in nano or vi on the command line, this process text appears as one line separated by carriage returns ^M.

GNU nano 5.6.1                           output_log_18_01_2024.log
+---------------------------------------------------------------------------+
Reading flash ............... 0x00000000 (0%) ^M Reading flash ............... 0x00001000 (0%) ^M Reading flash ............... 0x00002000 (0%) ^M Reading flash ............... 0x00003000 (0%) ^M Reading flash ............... 0x00004000 (0%) etc...

As such I am trying to use a python script to detect these carriage returns and process them accordingly. Here is a script I have tried:

import sys, re

f = open(sys.argv[1], "r")
data = f.read()

counter = 0
for char in data:
    print(char, end="")
    if char == r'\r':
        counter += 1
        
print(counter)
# always returns 0


rx = r'\r'
rr = re.search(rx, data)

print(rr)
# always returns None

f.close()

Why is python unable to see these carriage returns? Is it just interpretting them as new lines and there's not much I can do? I am open to any support in python or bash, basically anything that will let me remove the bulk of this log and retain the important text.

Edit: Removed images of errors, replaced with text copies.

Answer 1

Here's an answer that ended up working for me. There's probably a far more efficient way of doing this. but the script this is a part of is already very very slow.

# formatter.py

#!/usr/bin/python3

import sys

### Split at newlines.
testlist = repr(sys.argv[1]).split(r'\n')

for i in range(0, len(testlist)):

    line = testlist[i]
    if line[1] == " ":
        line = line.replace(" ","",1)
    ### If a return carriage is found in line
    if (line.find(r'\r') > -1):
        old_idx = 0
        curr_idx = line.find(r'\r', old_idx)
        ### Find last occurence of \r   
        while curr_idx != -1:
            old_idx = curr_idx
            curr_idx = line.find(r'\r', (old_idx+1))
        
        ### Return line from position of penultimate carriage return to end of line.
        print(line[old_idx+2:].replace(r'\r',""))
    ### If no carriage returns are found, return script as is.
    else:
        print(line)

# echoline.sh

#!/bin/bash

echoLine()
{
    outfile="test.txt"

    # get input
    set -f # stops * being expanded
    if test ! -t 0 # pipe
    then
        indata=$(</dev/stdin)
    elif test -n "$1"
    then
        indata="$@"
    fi

    indata="${indata//^M/'\r'}"
    IFS='$'; arrIN=($indata); unset IFS;

    for (( x=0; x<${#arrIN[@]}; x++))
    do
        outdata=$(python3 formatter.py "${arrIN[x]}" 2>/dev/null || python3 formatter.py "${arrIN[x]: -300}")
        outdata="${outdata//"'"/""} \n"
        echo -ne "$outdata" >> $outfile
        echo -ne "$outdata"
    done
}

echoLine -s $(cat -e output_log_18_01_2024_old.log)