Pretty Traceback

Human readable stacktraces for Python.

Project/Repo:

Code Quality/CI:

Overview

Pretty Traceback groups together what belongs together, adds coloring and alignment. All of this makes it easier for you to see patterns and filter out the signal from the noise. This tabular format is best viewed in a wide terminal.

In other words, get this 😍

Instead of this 🤮

Traceback (most recent call last):
  File "test/test_formatting.py", line 199, in <module>
    main()
  File "test/test_formatting.py", line 190, in main
    run_pingpong()
  File "test/test_formatting.py", line 161, in run_pingpong
    sched3.run()
  File "/home/mbarkhau/miniconda3/envs/pretty-traceback_py38/lib/python3.8/sched.py", line 151, in run
    action(*argument, **kwargs)
  File "/home/mbarkhau/miniconda3/envs/pretty-traceback_py38/lib/python3.8/sched.py", line 151, in run
    action(*argument, **kwargs)
  File "/home/mbarkhau/miniconda3/envs/pretty-traceback_py38/lib/python3.8/sched.py", line 151, in run
    action(*argument, **kwargs)
  File "test/test_formatting.py", line 151, in _ping
    _pong(depth + 1)
  File "test/test_formatting.py", line 129, in _pong
    _ping(depth + 1)
  File "test/test_formatting.py", line 136, in _ping
    sp.check_output(["command_that", "doesnt", "exist"])
  File "/home/mbarkhau/miniconda3/envs/pretty-traceback_py38/lib/python3.8/subprocess.py", line 411, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
  File "/home/mbarkhau/miniconda3/envs/pretty-traceback_py38/lib/python3.8/subprocess.py", line 489, in run
    with Popen(*popenargs, **kwargs) as process:
  File "/home/mbarkhau/miniconda3/envs/pretty-traceback_py38/lib/python3.8/subprocess.py", line 854, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/home/mbarkhau/miniconda3/envs/pretty-traceback_py38/lib/python3.8/subprocess.py", line 1702, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'command_that'

If your terminal is wide enough, the long paths are preserved.

Usage

Add the following to your __main__.py or the equivalent module which is your entry point.

try:
    import pretty_traceback
    pretty_traceback.install()
except ImportError:
    pass    # no need to fail because of missing dev dependency

Please do not add this code e.g. to your __init__.py or any other module that your users may import. They may not want you to mess with how their tracebacks are printed.

If you do feel the overwhelming desire to import the pretty_traceback in code that others might import, consider using the envvar argument, which will cause the install function to effectively be a noop unless you set ENABLE_PRETTY_TRACEBACK=1.

try:
    import pretty_traceback
    pretty_traceback.install(envvar='ENABLE_PRETTY_TRACEBACK')
except ImportError:
    pass    # no need to fail because of missing dev dependency

Note, that the hook is only installed if the existing hook is the default. Any existing hooks that were installed before the call of pretty_traceback.install will be left in place.

LoggingFormatter

A logging.Formatter subclass is also available (e.g. for integration with flask).

import os
from flask.logging import default_handler

try:
    if os.getenv('FLASK_DEBUG') == "1":
        import pretty_traceback
        default_handler.setFormatter(pretty_traceback.LoggingFormatter())
except ImportError:
    pass    # no need to fail because of missing dev dependency

More Examples

Alternatives

Pretty Traceback is heavily inspired by the backtrace module by nir0s but there are many others (sorted by github stars):

• https://github.com/qix-/better-exceptions
• https://github.com/cknd/stackprinter
• https://github.com/onelivesleft/PrettyErrors
• https://github.com/skorokithakis/tbvaccine
• https://github.com/aroberge/friendly-traceback
• https://github.com/HallerPatrick/frosch
• https://github.com/nir0s/backtrace
• https://github.com/staticshock/colored-traceback.py
• https://github.com/chillaranand/ptb
• https://github.com/laurb9/rich-traceback
• https://github.com/willmcgugan/rich#tracebacks

Contributors

Changelog for https://github.com/mbarkhau/pretty-traceback

2020.1016

• Shorten tracebacks for RecursionError

2020.1012

• Improve alias selection

2020.1011

• Fix github #1: Invalid path handling for ./script.py

2020.1010

• Fix gitlab #5: Only show aliases that were actually used.
• Fix gitlab #5: Better alignment on narrow terminals.

2020.1009

• Fix gitlab #3: Corner case where exception has None as context.
• Fix gitlab #2: Improve formatting when line overflows.

2020.1008

• Add pretty_traceback.LoggingFormatter

2020.1006

• Add wide mode.

2020.1005

• Update formatting to work better with recursive calls.
• Add tests

2020.1001

• Initial release