backtrace

WIP! Untested!

backtrace manipulates Python tracebacks to make them more readable. It provides different configuration options for coloring and formatting.

backtrace also allows to choose the formatting of each part of the traceback; show the traceback entries in reversed order, and more..

Examples:

When piping to backtrace:

When using the API directly from Python:

NOTE: Didn't test this on Windows yet. Should work.. but don't know how well.

Alternatives

• colored_traceback provides a way to color your tracebacks to make them more readable. It's a nice little tool but lacks actually re-formatting the traceback which is what the biggest problem is from my POV.
• Um.. your own implementation? There's really a reason for me doing this. I do have a life you know (well.. I try anyway).

Installation

backtrace officially supports Linux and OSX on Python 2.7 and 3.4+. Python 2.6 will also probably work, but with no guarantees.

pip install backtrace

For dev:

pip install https://github.com/nir0s/backtrace/archive/master.tar.gz

Usage

backtrace provides two methods for manipulating your tracebacks.

• Piping to backtrace using its CLI
• Using backtrace from within your code

Piping

You can pipe stderr into backtrace which will try to detect a traceback, parse it and display a beautified trace.

$ backtrace -h
usage: backtrace [-h] [-r] [-a] [-s] [-c]

Beautify Tracebacks.

Just pipe stderr into backtrace like so:
  `python bad-program.py 2>&1 | backtrace`

optional arguments:
  -h, --help          show this help message and exit
  -r, --reverse       Reverse traceback entry order
  -a, --align         Right-align the backtrace
  -s, --strip-path    Strip the path to the module
  -c, --conservative  Activate conservative mode

$ python my-traceback-generating-program.py 2>&1 | backtrace
...

Inside your application

import backtrace

backtrace.hook(
    reverse=False,
    align=False,
    strip_path=False,
    enable_on_envvar_only=False,
    on_tty=False,
    conservative=False,
    styles={})

# more code...

# if you wanna restore the default hook...
backtrace.unhook()
...

You can pass the following flags to hook to change backtrace's behavior:

• If reverse is True, the traceback entries will be printed in reverse order.
• If align is True, all parts (line numbers, file names, etc..) will be aligned to the left according to the longest entry. This allows for extended readability as your eyes don't have to move between columns to understand what's going on.
• If strip_path is True, only the file name will be shown, not its full path. This is useful when you know you're running in the context of a single module or a single package containing only a root folder so you only need file names. This can help keep the traceback clean.
• If enable_on_envvar_only is True, only if the environment variable ENABLE_BACKTRACE is set, backtrace will be activated.
• If on_tty is True, backtrace will be activated only if you're running in a real terminal (i.e. not piped, redirected, etc..). This can help keep the original traceback when logging to files or piping to look for information.
• styles is a dictionary containing the styling for each part of the rebuilt traceback. See below.
• If conservative is true, a more conservative format will be provided for people who find the default backtrace style too new or intimidating. For example, no alignment will be done (unless align is explicitly passed), styles will be ignored, and potential unnecessary data will be retained. Try It! It's still eye-candy.

Styles

Styles allow you to customize the coloring and structure of your new traceback. The defaults are:

STYLES = {
    'backtrace': Fore.YELLOW + '{0}',
    'error': Fore.RED + Style.BRIGHT + '{0}',
    'line': Fore.RED + Style.BRIGHT + '{0}',
    'module': '{0}',
    'context': Style.BRIGHT + Fore.GREEN + '{0}',
    'call': Fore.YELLOW + '--> ' + Style.BRIGHT + '{0}',
}

Where:

• backtrace is the main traceback message.
• error is the error message presenting the exception message and its type.
• line is the line number of each entry.
• module is the calling module of each entry.
• context is the calling function/method of each entry.
• call is the called function/method/assignment of each entry.

and the {0} format place holder is the actual value of the field.

Sending a partial dictionary containing changes in only some parts of the traceback will have backtrace use the defaults for whatever wasn't specified.

You can do all sorts of stuff like removing a certain field by setting the formatting of that field to an empty string; add more verbose identifiers to each field by appending an ID in front of it or just adding paranthese around a field.

Coloring

Coloring is powered by colorama.

Testing

To see an example printout:

$ python test.py

git clone [email protected]:nir0s/backtrace.git
cd backtrace
pip install tox
tox

Contributions..

See CONTRIBUTIONS

Pull requests are always welcome..