How to output color using argparse in python if any errors happen?

Question

Is there a way to make argparse to output error or warning with colors of red or orange?

I know there are some OS standard colors can be used directly, like "\033[38;5;196m" (red-like) or "\033[38;5;208m" (orange-like), but is there a way to use them or something similar into argparse? Messages with different colors are really helpful for people to recognize if any thing happens.

Answer 1

I just thought of the same question and decided I would poke around the argparse module because the output was kinda weird (On Linux, the words 'error' and 'usage' are usually capitalized, and I also wanted errors to be printed in bold red throughout my program, including when command line arguments were checked.) Here is my code for some nicer looking output, tested using Python 3.6.3 (I really just included more colors as an example here, when in practice you should only need the bold red for errors).

import argparse
import sys
from gettext import gettext

class ColoredArgParser(argparse.ArgumentParser):

    # color_dict is a class attribute, here we avoid compatibility
    # issues by attempting to override the __init__ method
    # RED : Error, GREEN : Okay, YELLOW : Warning, Blue: Help/Info 
    color_dict = {'RED' : '1;31', 'GREEN' : '1;32', 
                  'YELLOW' : '1;33', 'BLUE' : '1;36'}

    def print_usage(self, file = None):
        if file is None:
            file = sys.stdout
        self._print_message(self.format_usage()[0].upper() + 
                            self.format_usage()[1:],
                            file, self.color_dict['YELLOW'])

    def print_help(self, file = None):
        if file is None:
            file = sys.stdout
        self._print_message(self.format_help()[0].upper() +
                            self.format_help()[1:],
                            file, self.color_dict['BLUE'])

    def _print_message(self, message, file = None, color = None):
        if message:
            if file is None:
                file = sys.stderr
            # Print messages in bold, colored text if color is given.
            if color is None:
                file.write(message)
            else:
                # \x1b[ is the ANSI Control Sequence Introducer (CSI)
                file.write('\x1b[' + color + 'm' + message.strip() + '\x1b[0m\n')

    def exit(self, status = 0, message = None):
        if message:
            self._print_message(message, sys.stderr, self.color_dict['RED'])
        sys.exit(status)

    def error(self, message):
        self.print_usage(sys.stderr)
        args = {'prog' : self.prog, 'message': message}
        self.exit(2, gettext('%(prog)s: Error: %(message)s\n') % args)