How to print text with specific format to a printer in Python?

I am printing a text string to a printer like so:

import os

string_value = 'Hello, World!'

printer = os.popen('lpr -P Canon_iP110_series', 'w')
printer.write(string_value)
printer.close()

This works perfectly, printing the text to the printer in what I assume is the default font/color (black).

I want to change some features of the text, though. For example, I want to bold the word 'Hello', perhaps, or print 'World' in green maybe.

I have found several answers having to do with "printing" text, but they're giving escape codes relating to the terminal/console output - not to a printer. Eg, How can I print bold text in Python?

These escape codes do work when I print the string to the console. Eg,

bold_on = '\033[1m'
bold_off = '\033[0m'

string_value = '{0}Hello{1}, World!'.format(bold_on, bold_off)

print(string_value)

does output:

Hello, World!

to the console. However, it does not bold the 'Hello' text on the printer.

How can I bold text at least, and possibly change other font attributes, when printing text to a printer in Python?

(Python 3.9+)

Solution

As @chepner commented, it seems Python is pretty basic when it comes to printing text to a printer. What I ended up doing instead is using FPDF v1.7.2 to place the text in a PDF file. Sending the file to the printer, then, outputs the text with the attributes I defined.

The FPDF-related functions in my example should work the same on all platforms.
The printer-related functions in this example should work on macOS and Linux. Windows would require different methods for printing.

import os  # for printing to printer
from fpdf import FPDF  # for pdf creation

# set up pdf basics:
pdf = FPDF('P', 'pt', 'Letter')  # P(ortrait), points size ref, Letter-size paper
pdf.add_page()  # add a blank page to start
pdf.set_font('helvetica', size=12)  # optional here, but useful if most text is plain

hello_string = 'Hello'
world_string = ', World!'

# set font to B(old) *and* I(talic)
pdf.set_font('helvetica', size=12, style='BI')

# write string into PDF page, stopping at end of string; line height = 6 pts
pdf.write(h=6, txt=hello_string)

# change back to regular font
pdf.set_font('helvetica', size=12)

# write rest of string into PDF
pdf.write(h=6, txt=world_string)


# output the created page(s) as a PDF file
pdf_filename = 'hello_world.pdf'
pdf.output(pdf_filename)


# finally, print the PDF file to the printer
printer_name = 'Canon_iP110_series'
printer_string = 'lpr -P {0} {1}'.format(printer_name, pdf_filename)
os.system(printer_string)

Notes:

I had to play with line heights to resolve some overlapping
Some FPDF functions allow for \n line breaks in the string, while others don't. write does allow for line breaks and will stop wherever the string stops. The next write function begins where the last one stopped.
FPDF also has functions to set text color - among some other interesting features
FPDF documentation has moved around. I found a number of examples with a search. As of 17 March 2023, I was able to access Reingart's FPDF tutorial on GitHub, which gives some great examples
To locate the desired printer name, use lpstat (note the -d is optional; when the -d is used, lpstat also displays which printer is set as default):

lpstat -p [-d]

UPDATE (November 2024): There's an updated fork of fpdf that's up-to-date and well-maintained. It's called fpdf2, and it's at version 2.8.1 as of this writing.