Skip to main content

Adds variables to python traceback. Simple, lightweight, controllable. Debug reasons of exceptions by logging or pretty printing colorful variable contexts for each frame in a stacktrace, showing every value. Dump locals environments after errors to console, files, and loggers.

Project description

Example

Python Traceback (Error Message) Printing Variables

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

Actions Status Codecov License: MIT PyPI PyPI Annotations coverage No-OOP coverage Dependencies Gitter


“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


Installation

pip install traceback-with-variables

Quick Start

Simplest usage, for the whole program:

    from traceback_with_variables import activate_by_import

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

traceback-with-variables ...script/tool/module with arguments...

Decorator, for a single function:

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

Context, for a single code block:

    with printing_tb():

Work with traceback lines in a custom manner:

    return '\n'.join(iter_tb_lines(e))

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

    with printing_tb(file_=LoggerAsFile(logger)):
    # or
    @prints_tb(file_=LoggerAsFile(logger)): 

Colors

Example

How does it save my time?

  • 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 = 0
    builtins.ZeroDivisionError: division by zero
    
  • Automate your logging too:

    logger = logging.getLogger('main')
    
    def main():
        ...
        with printing_tb(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 main
    2020-03-30 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 = 300
    2020-03-30 18:24:31 main ERROR       w1 = 200
    2020-03-30 18:24:31 main ERROR       h2 = 300
    2020-03-30 18:24:31 main ERROR       w2 = 0
    2020-03-30 18:24:31 main ERROR   File "./temp.py", line 10, in get_avg_ratio
    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       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 = 300
    2020-03-30 18:24:31 main ERROR       w = 0
    2020-03-30 18:24:31 main ERROR   File "./temp.py", line 13, in get_ratio
    2020-03-30 18:24:31 main ERROR     return height / width
    2020-03-30 18:24:31 main ERROR       height = 300
    2020-03-30 18:24:31 main ERROR       width = 0
    2020-03-30 18:24:31 main ERROR builtins.ZeroDivisionError: division by zero
    
  • Free your exceptions of unnecessary information load:

    def make_a_cake(sugar, eggs, milk, flour, salt, water):
        is_sweet = sugar > salt
        is_vegan = not (eggs or milk)
        is_huge = (sugar + eggs + milk + flour + salt + water > 10000)
        if not (is_sweet or is_vegan or is_huge):
            raise ValueError('This is unacceptable, guess 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.


  • 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.

Examples and recipes

Reference

All functions have output customization

  • max_value_str_len max length of each variable string
  • max_exc_str_len max length of exception, should variable print fail
  • num_context_lines number of lines around the target code line to print
  • ellipsis_ string to denote long strings truncation, default=...
  • file_ where to print exception, a file or a wrapped logger, default=sys.stderr i.e. usual printing to console
  • color_scheme one of ColorSchemes: .none (by default), .common, .synthwave

activate_by_import

Just import it. No arguments, for real quick use.

from traceback_with_variables import activate_by_import

override_print_tb

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

def main():
    override_print_tb(...)

prints_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_tb
def f(...):

@prints_tb(...)
def f(...):

printing_tb

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 the with scope. Program exiting due to unhandled exception still prints a usual traceback.

with printing_tb(...):

LoggerAsFile

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


iter_tb_lines

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

Project details


Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

traceback-with-variables-1.1.7.tar.gz (13.9 kB view hashes)

Uploaded Source

Built Distribution

traceback_with_variables-1.1.7-py3-none-any.whl (12.5 kB view hashes)

Uploaded Python 3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page