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Format tracebacks better.

Project description

Note: This is a still an early pre-release. It works for me except for some ugliness with SyntaxErrors, but there are no guarantees.

Tracefront makes your tracebacks pretty and useful, like in nose-progressive:

(The FAIL bits and test names, of course, are just part of that testrunner.)

What’s my motivation?

  • Judicious use of color and other formatting makes the traceback easy to scan. It’s especially easy to slide down the list of function names to keep your place while debugging.

  • Using relative paths (optional) and omitting redundant wording fits much more in limited screen space.

  • Editor shortcuts (see below) let you jump right to any problem line in your editor.

Editor Shortcuts

For each frame of a traceback, Tracefront provides an editor shortcut. This is a combination of a filesystem path and line number in a format understood by vi, emacs, the BBEdit command-line tool, and a number of other editors:

vi +361 apps/notifications/  # test_notification_completeness

Just triple-click (or what have you) to select the line, and copy and paste it onto the command line. You’ll land right at the offending line in your editor of choice. As a bonus, the editor shortcut is more compact than the stock traceback formatting, which is handy if you have something like a test runner printing a lot of them. If it looks like the output is going to a capable terminal, it’ll even use color.

You can set which editor to use by setting either of these, which Tracefront checks in order:

  • The $TRACEFRONT_EDITOR environment variable

  • The $EDITOR environment variable


Just do this…

pip install tracefront

…and all your tracebacks will be pretty and helpful for any app that does this:

imports traceback

In the future, I’m thinking about using even deeper evil to make it active even more implicitly.


Tracefront is configured by setting environment variables.


Set this to 1 to always use absolute paths rather than ones relative to the current working directory.


The editor to use when building editor shortcuts


ANSI color number to use for function names in tracebacks


ANSI color number to use for de-emphasized text (like editor shortcuts) in tracebacks

How It Works

Tracefront shadows the stock traceback module, calling through for most stuff but replacing the core formatting bits. If a program makes assumptions about the composition of formatted tracebacks, it might break, but that would be weird, since there are more convenient representations easily available.


Tracefront is under the MIT License. See the LICENSE file.

Version History

0.4 (2012-07-08)
  • Make TRACEFRONT_FUNCTION_COLOR and TRACEFRONT_DIM_COLOR work as advertised. (msabramo)

  • Make tests run under Python 2.5. (msabramo)

  • Add Travis CI. (msabramo)

  • Work around spurious python test error message. (msabramo)

0.3 (2012-03-22)
  • Grab the current working directory earlier so we’re more likely to get the relative paths right (like when running nosetests).

  • Whip tox into shape. Tests now pass under Python 2.5.

  • Install more thoroughly. This should catch tracebacks thrown by the interpreter itself, not just ones explicitly formatted–as long as the program imports the traceback module at some point.

  • Patch print_list(), the last major routine that needed to be prettified. We still need to polish up display of the last few lines of SyntaxErrors.

0.2 (2012-03-17)
  • Use terminal codes all the time. (Django uses format_list instead of print_tb, but I want it to be in color anyway.)

  • Document all the options in the readme.

0.1 (2012-03-16)
  • Pulled the traceback formatting stuff out of nose-progressive. Barely tested at all. Will probably erase your drive.

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