What’s the recommended way to print output to stderr in Python?

General Discussions
,
1

I’m trying to understand the best way to send output to stderr in Python instead of the usual standard output. I’ve come across multiple ways to python print to stderr, and I’m a bit confused about how they differ and which approach is preferred in modern Python code.

I’ve seen examples that use different techniques, some of which seem version-specific or lower-level than others. For example, approaches using sys.stderr, direct OS writes, or even special syntax in older Python versions.

Here are a few rewritten examples of the kinds of methods I’ve encountered:

import sys

print("error message", file=sys.stderr)

import sys

sys.stderr.write("error message\n")

import os

os.write(2, b"error message\n")

I’m trying to figure out:

  • What are the practical differences between these methods?
  • Are some of them outdated or discouraged?
  • Which approach should generally be used for clean, readable, and portable code when printing errors or logs?

Any guidance on best practices for printing to stderr in Python would be really helpful. Thanks!

2

From my experience, the most straightforward and readable way to print to stderr in Python is using the print function with the file argument:

import sys
print("Something went wrong!", file=sys.stderr)

This is fully supported in Python 3, looks clean, and behaves just like normal print but redirects output to stderr. I personally use this in scripts and CLI tools because it’s very readable for anyone maintaining the code later.

3

Another approach I’ve used, especially when you need finer control over formatting or avoiding automatic newline characters, is sys.stderr.write:

import sys
sys.stderr.write("Something went wrong!\n")

This method doesn’t append a newline automatically, so you have to add \n yourself. I find it useful in logging-heavy scripts or when you want to mix output formatting without relying on print. It’s slightly lower-level but very portable across Python versions.

4

I’ve seen some older examples using os.write:

import os
os.write(2, b"Something went wrong!\n")

This works, but it’s very low-level and requires byte strings. I usually only consider this when writing extremely performance-sensitive scripts where avoiding Python buffering matters, which is rare. For everyday scripts, I wouldn’t recommend it because it’s less readable and more error-prone.