How do I print an exception in Python?

The overachievers' way: traceback

Had more complicated errors before and have a hangover, I mean, a traceback? traceback.print_exc() is the aspirin of Python functions, providing a much-needed context of that menacing error.

import traceback

try:
    # Daredevil code here
except Exception as e:
    traceback.print_exc()  # Never mind solving. I mean, "dissolving". Just print it.
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This prints the stack trace, so you can finally see what's been wreaking havoc behind the scenes.

Pro tip: logging exceptions

Why print when you can LOG (perhaps to complain later to a friend)? Utilize Python's logging module for your gripes... I mean, exceptions, of course!

import logging

try:
    # some risky operation
except Exception as e:
    logging.exception("Error just chilling here:")
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logging.exception() gives a detailed account of the culprit traceback. Next time, errors won't just sneak past your code.

Exception alert: sys.stderr

Errors can be sneaky. Let's get them in the spotlight by directing them to sys.stderr, like an MC announcing a not-so-popular guest:

import sys

try:
    # a bit of specious code
except Exception as e:
    print(f"Alert! Found an error: {e}", file=sys.stderr)  # The spotlight's on you, Error!
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Using sys.stderr makes sure your errors don’t duck into the anonymity of your standard output.

Turn the dial up: advanced debugging

Full error profile with sys.exc_info()

Hair pulling over not having enough error info? Have some more! sys.exc_info() hands you the type, value, and a backtrace of the exception:

import sys

try:
    # a failing piece of code
except:
    exc_type, exc_value, exc_traceback = sys.exc_info()
    print(f"Exception type: {exc_type.__name__}, Value: {exc_value}", file=sys.stderr)
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It's like your error's resumé. Enough for an interview, wouldn't you agree?

Chain of blunders: exception chaining

Like a perfect storm of errors leading to a catastrophe, Python 3 introduced exception chaining, letting us foresee a storm before it hits:

try:
    # initial tricky operation
    except IOError as intermediate_exception:
    try:
        # retrying operation
    except FileNotFoundError as final_exception:
        raise RuntimeError('Both operations failed') from final_exception
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Just like dominos, one error leading to another. How elegant!

World-class bug hunter: catch all exceptions

Think you've seen all kinds of errors? Think again! Here's a way to catch all exceptions, even keyboard interrupts:

try:
    # code that must keep running
except BaseException as e:
    logging.critical('We caught an alien! I mean...unforeseen exception.', exc_info=True)
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Gotta catch 'em all! (But please, use with caution. You don't want to catch a virus, do you?)