在 Windows 上使用 tee 时如何保留 python colorama 颜色输出

Question

In my Windows 10 scenario, I want to print arbitrary python console output ( print() , sys.exit() , etc) both to console and a log file. I don't have control over some parts of the code (external python packages), so I cannot use some dedicated logging mechanism.

After some research I found the tool tee.exe in UnxUtils which does this task almost the way I want.

My problem is to preserve color as generated by python's colorama package. Is there any way to accomplish that? Currently, tee.exe strips away the color.

The answer I am looking does not have to rely on tee.exe, it's just the closest I got to a real solution. What I am looking for should do the following:

• any command line output appears both in the command line and the log file (both STOUT and STDERR)
• the output appears on the command line in real time. Bonus points if this is also true for the log file.
• color is preserved on the command line. Bonus points if the log file does not contain any color-related artifacts.

What I have so far is this:

Python file teetest.py :

import sys
import colorama

print("Test")
print("2nd Test")

colorama.init(autoreset=True)
print(colorama.Fore.RED + 'Color Test')
colorama.deinit(autoreset=True)

sys.exit("Error_Test")

Batch file teetest.bat :

@echo off
python teetest.py 2>&1 | tee log.txt
pause

My output looks like this (command line and log file are identical, no color):

Test
2nd Test
Color Test
Error_Test

The solution I am looking for will print the above to the command line so the words Color Test are red.

Edit:

It seems that tee.exe is not at fault. Instead, colorama strips away the ANSI characters for color control by design, so the color is lost when passed through tee.exe .

From the colorama manual:

Colorama makes this work on Windows, too, by wrapping stdout, stripping ANSI sequences it finds (which would appear as gobbledygook in the output), and converting them into the appropriate win32 calls to modify the state of the terminal.

Colorama's init() function offers the parameter strip , which if False , does cause colorama to not strip away the ANSI characters. This in turn allows to write a custom tee.py that does the same as tee.exe , as outlined by user @martineau below. In it, we can call colorama and handle the color properly.

This might be a workable solution, but it still has the downside that I would have to replace all colorama init() calls with init(strip=False) in my original python code and that in turn would cause ANSI characters to appear in the output if the code was called without redirecting through tee.py .

This might actually be the closest we can get to a proper solution here. If anyone can offer other ideas, I'm all ears but I fear chances are slim.

Answer 1

I don't know how it will work with respect to colorama , but after being unsatisfied with several tee utilities for Windows that I found online, I ended up writing my own in Python (3.x).

You may have to modify it to suit your own needs, but it should be a good start.

mytee.py :

"""
    Copies stdin to stdout (screen) *and* the specified file.
"""
import fileinput
import os
from pathlib import Path
import sys

SHOW_FULL_PATH = False
DIVIDER = True
DIV_CH = ' '

if len(sys.argv) != 2:
    raise SystemExit('Usage: mytee <filepath>')

try:
    inp = fileinput.input(())  # Read from stdin.
    path = Path(sys.argv[1])
    stdout_write = sys.stdout.write
    stdout_flush = sys.stdout.flush
    # Assumes .py in same dir as output file.
    script = (f'{path.parent/path.stem}{path.suffix}' if SHOW_FULL_PATH else
              f'{path.stem}{path.suffix}')

    with open(path, 'w') as outp:  # Write to specified file.
        outp_write = outp.write
        outp_flush = outp.flush

        def write(line):
            stdout_write(line)
            outp_write(line)

        def writeln(line):
            write(line + '\n')

        banner = f'"{script}"' if ' ' in script else f'-[{script}]-'
        writeln(f'{banner}')
        if DIVIDER:
            writeln(f'{DIV_CH * len(banner)}')
        for line in inp:
            write(line)
        if DIVIDER:
            writeln(f'{DIV_CH * len(banner)}')
        writeln('-[done]-')
finally:
    inp.close()  # Not sure this is really necessary.

sys.exit(0)