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Very simple to use and fast, but versatile when needed. Try for debug and keep for small-scale production.

“It is useless work that darkens the heart.”– Ursula K. Le Guin

Tired of useless job of putting all your variables into debug exception messages? Just stop it.Automate it and clean your code. Once and for all.

Contents:Installation |🚀 Quick Start|Colors|How does it save my time? |Examples and recipes |Reference|FAQ

⚠️I'm open to update this module to meet new use cases and to make using it easier and fun: so any proposal or advice or warning is very welcome and will be taken into account of course. When I started it I wanted to make a tool meeting all standard use cases. I think in this particular domain this is rather achievable, so I'll try. Notenext_version branch also. Have fun!

pip install traceback-with-variables==2.2.1

conda install -c conda-forge traceback-with-variables=2.2.1

to use shortertb alias in interactive mode call this once:

python3 -c 'from traceback_with_variables.tb_alias import create_tb_alias as c; c()'

Using without code editing,running your script/command/module:

traceback-with-variables tested_script.py ...srcipt's args...

Simplest usage, for the whole program:

fromtraceback_with_variablesimportactivate_by_import

or just (if you added an alias by the above command)

importtb.a

Decorator, for a single function:

@prints_exc# def main(): or def some_func(...):

Context, for a single code block:

withprinting_exc():

Work with traceback lines in a custom manner:

lines=list(iter_exc_lines(e))

No exception but you want to print the stack anyway?:

print_cur_tb()

Using a logger [with a decorator,with a context]:

withprinting_exc(file_=LoggerAsFile(logger)):# or    @prints_exc(file_=LoggerAsFile(logger)):

Print traceback in interactive mode after an exception:

    >>> print_exc()

Customize any of the previous examples:

fromtraceback_with_variablesimportfmtfmt.max_value_str_len=10000fmt.skip_files_except='my_project'fmt.custom_var_printers= []# show all variables, no skips, no hides

• Turn a code totally covered by debug formatting from this:

    def main():      sizes_str = sys.argv[1]      h1, w1, h2, w2 = map(int, sizes_str.split())-     try:          return get_avg_ratio([h1, w1], [h2, w2])-     except:-         logger.error(f'something happened :(, variables = {locals()[:1000]}')-         raise-         # or-         raise MyToolException(f'something happened :(, variables = {locals()[:1000]}')            def get_avg_ratio(size1, size2):-     try:          return mean(get_ratio(h, w) for h, w in [size1, size2])-     except:-         logger.error(f'something happened :(, size1 = {size1}, size2 = {size2}')-         raise-         # or-         raise MyToolException(f'something happened :(, size1 = {size1}, size2 = {size2}')  def get_ratio(height, width):-     try:          return height / width-     except:-         logger.error(f'something happened :(, width = {width}, height = {height}')-         raise-         # or-         raise MyToolException(f'something happened :(, width = {width}, height = {height}')

  into this (zero debug code):

  + from traceback_with_variables import activate_by_import  def main():      sizes_str = sys.argv[1]      h1, w1, h2, w2 = map(int, sizes_str.split())      return get_avg_ratio([h1, w1], [h2, w2])            def get_avg_ratio(size1, size2):      return mean(get_ratio(h, w) for h, w in [size1, size2])  def get_ratio(height, width):      return height / width

  And obtain total debug info spending 0 lines of code:

  Traceback with variables (most recent call last):  File "./temp.py", line 7, in main    return get_avg_ratio([h1, w1], [h2, w2])      sizes_str = '300 200 300 0'      h1 = 300      w1 = 200      h2 = 300      w2 = 0  File "./temp.py", line 10, in get_avg_ratio    return mean([get_ratio(h, w) for h, w in [size1, size2]])      size1 = [300, 200]      size2 = [300, 0]  File "./temp.py", line 10, in <listcomp>    return mean([get_ratio(h, w) for h, w in [size1, size2]])      .0 = <tuple_iterator object at 0x7ff61e35b820>      h = 300      w = 0  File "./temp.py", line 13, in get_ratio    return height / width      height = 300      width = 0builtins.ZeroDivisionError: division by zero

• Automate your logging too:

  logger=logging.getLogger('main')defmain():    ...withprinting_exc(file_=LoggerAsFile(logger))        ...

  2020-03-30 18:24:31 main ERROR Traceback with variables (most recent call last):2020-03-30 18:24:31 main ERROR   File "./temp.py", line 7, in main2020-03-30 18:24:31 main ERROR     return get_avg_ratio([h1, w1], [h2, w2])2020-03-30 18:24:31 main ERROR       sizes_str = '300 200 300 0'2020-03-30 18:24:31 main ERROR       h1 = 3002020-03-30 18:24:31 main ERROR       w1 = 2002020-03-30 18:24:31 main ERROR       h2 = 3002020-03-30 18:24:31 main ERROR       w2 = 02020-03-30 18:24:31 main ERROR   File "./temp.py", line 10, in get_avg_ratio2020-03-30 18:24:31 main ERROR     return mean([get_ratio(h, w) for h, w in [size1, size2]])2020-03-30 18:24:31 main ERROR       size1 = [300, 200]2020-03-30 18:24:31 main ERROR       size2 = [300, 0]2020-03-30 18:24:31 main ERROR   File "./temp.py", line 10, in <listcomp>2020-03-30 18:24:31 main ERROR     return mean([get_ratio(h, w) for h, w in [size1, size2]])2020-03-30 18:24:31 main ERROR       .0 = <tuple_iterator object at 0x7ff412acb820>2020-03-30 18:24:31 main ERROR       h = 3002020-03-30 18:24:31 main ERROR       w = 02020-03-30 18:24:31 main ERROR   File "./temp.py", line 13, in get_ratio2020-03-30 18:24:31 main ERROR     return height / width2020-03-30 18:24:31 main ERROR       height = 3002020-03-30 18:24:31 main ERROR       width = 02020-03-30 18:24:31 main ERROR builtins.ZeroDivisionError: division by zero

• Free your exceptions of unnecessary information load:

  defmake_a_cake(sugar,eggs,milk,flour,salt,water):is_sweet=sugar>saltis_vegan=not (eggsormilk)is_huge= (sugar+eggs+milk+flour+salt+water>10000)ifnot (is_sweetoris_veganoris_huge):raiseValueError('This is unacceptable, look why!')    ...

• — Should I use it after debugging is over, i.e.in production?

  Yes, of course! That way it might save you even more time (watch out for sensitive datalike 🔴passwords andtokens in you logs). Note: you can deploy more serious monitoring frameworks, e.g.Sentry

• Stop this tedious practice in production:

  step 1: Notice some exception in a production service.
  step 2: Add more printouts, logging, and exception messages.
  step 3: Rerun the service.
  step 4: Wait till (hopefully) the bug repeats.
  step 5: Examine the printouts and possibly add some more info (then go back to step 2).
  step 6: Erase all recently added printouts, logging and exception messages.
  step 7: Go back to step 1 once bugs appear.

• — Is it fast? I have huge lists and dicts and data objects!

  Data size doesn't matter! Printing is smart, so only visible data portions are inpsected, e.g.

  list(range(100000000)) becomes just"[0, 1, 2, ...9998, 99999999]" in 0.00012s

  Usefmt's.max_value_str_len, and.ellipsis_rel_pos (0.0 to 1.0) to tweak the output.

• run python code without changes: a script, a module, a commnad
• simple usage
• simple usage in Jupyter or IPython
• print current stack, when there's no exception
• print last exception in Python console
• manually change global printer
• manually change global printer in Jupyter or IPython
• working with a function
• working with a function, logging
• working with a code block
• working with a code block, logging
• get traceback lines for custom things
• using withflask
• customize the output
• passwords and tokens in logs

• max_value_str_len max length of each variable string, -1 to disable, default=1000
• objects_details depth of details of objects inspection
• ellipsis_rel_pos when truncating long strings where to put the "...", from 0.0 to 1.0, default=0.7
• max_exc_str_len max length of exception, should variable print fail, -1 to disable, default=10000
• before number of code lines before the raising line, default=0
• after number of code lines after the raising line, default=0
• ellipsis_ string to denote long strings truncation, default=...
• skip_files_except use to print only certain files; list of regexes, ignored if empty, default=None
• brief_files_except use to print variables only in certain files; list of regexes, ignored if empty, default=None
• custom_var_printers list of pairs of (filter, printer); filter is a name fragment, a type or a function or a list thereof; printer returnsNone to skip a var, standard ones arehide,skip,show
• color_scheme isNone or one ofColorSchemes:.none ,.common,.nice,.synthwave.None is for auto-detect

Just import it. No arguments, for real quick use in regular Python.

fromtraceback_with_variablesimportactivate_by_import

Just import it. No arguments, for real quick use in Jupyter or IPython.

fromtraceback_with_variablesimportactivate_in_ipython_by_import

Call once in the beginning of your program, to change how traceback after an uncaught exception looks.

defmain():override_print_exc(...)

Call once in the beginning of your program, to change how traceback after an uncaught exception looks.

defmain():override_print_exc(...)

Prints traceback for a given/current/last (first being notNone in the priority list) exception to a file, default=sys.stderr. Convenient for manual console or Jupyter sessions or custom try/except blocks. Note that it can be called with a given exception value or it can auto discover current exception in anexcept: block or it can auto descover last exception value (long) aftertry/catch block.

print_exc()

Prints current traceback when no exception is raised.

print_cur_tb()

Function decorator, used for logging or simple printing of scoped tracebacks with variables. I.e. traceback is shorter as it includes only frames inside the function call. Program exiting due to unhandled exception still prints a usual traceback.

@prints_excdeff(...):@prints_exc(...)deff(...):

Context manager (i.e.with ...), used for logging or simple printing of scoped tracebacks with variables. I.e. traceback is shorter as it includes only frames inside thewith scope. Program exiting due to unhandled exception still prints a usual traceback.

withprinting_exc(...):

A logger-to-file wrapper, to pass a logger to print tools as a file.

Iterates the lines, which are usually printed one-by-one in terminal.

Likeiter_exc_lines but returns a single string.

Likeiter_exc_lines but doesn't need an exception and prints upper frames..

Likeiter_cur_tb_lines but returns a single string.

• In Windows console crash messages have no colors.

  The default Windows console/terminal cannot print [so calledansi] colors, but this isfixable, especially with modern Windows versions. Therefore colors are disabled by default,but you can enable them and check if it works in your case.You can force enable colors by passing--color-scheme common (for complete list of colors pass--help) console argument.

• Windows console prints junk symbols when colors are enabled.

  The default Windows console/terminal cannot print [so calledansi] colors, but this isfixable, especially with modern Windows versions. If for some reason the colors are wrongly enabled by default,you can force disable colors by passing--color-scheme none console argument.

• Bash tools like grep sometimes fail to digest the output when used with pipes (|) because of colors.

  Please disable colors by passing--color-scheme none console argument.The choice for keeping colors in piped output was made to allow convenient usage ofhead,tail, file redirection etc.In cases like| grep it might have issues, in which case you can disable colors.

• Output redirected to a file in> output.txt manner has no colors when Icat it.

  This is considered a rare use case, so colors are disabled by default when outputting to a file.But you can force enable colors by passing--color-scheme common (for complete list of colors pass--help) console argument.

• activate_by_import orglobal_print_exc don't work in Jupyter or IPython as if not called at all.

  In Jupyter or IPython you should useactivate_in_ipython_by_import orglobal_print_exc_in_ipython. IPython handles exceptions differently than regular Python.

• The server framework (flask,streamlit etc.) still shows usual tracebacks.

  In such frameworks tracebacks are printed not while exiting the program (the program continues running), hence you should override exception handling in a mannerproper for the given framework. Please address theflask example.

• How do I reduce output? I don't need all files or all variables.

  Useskip_files_except,brief_files_except,custom_var_printers to cut excess output.

• I have ideas about good colors.

  Please fork, add a newColorScheme toColorSchemesand create a Pull Request tonext_version branch.Choose the color codes and visuallytest it likepython3 -m traceback_with_variables.main --color-scheme {its name} examples/for_readme_image.py.

• My code doesn't work.

  Pleasepost your case. You are very welcome!

• Other questions or requests to elaborate answers.

  Pleasepost your question or request. You are very welcome!