Adds variables to python traceback. Simple, lightweight, controllable. Debug reasons of exceptions by pretty printing variable contexts for each frame in a stacktrace, showing every value. Dump locals environments after errors to console, files, and loggers.
Project description
Python traceback (stacktrace) printing variables.
Very simple to use, but versatile when needed.
Quick Start
Simplest usage:
from traceback_with_variables import activate_by_import
Decorator:
@prints_tb
# def main(): or def some_func(...):
Context:
with printing_tb():
Work with traceback lines:
return '\n'.join(iter_tb_lines(e))
Using a logger:
with printing_tb(file_=LoggerAsFile(logger)):
# or
@prints_tb(file_=LoggerAsFile(logger)):
Installation
pip install traceback-with-variables
Rationale
-
Tired of putting all your variables in debug exception messages? Just stop it. Go clean your code:
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 = {variables()[:1000]}') - raise - # or - raise MyToolException(f'something happened :(, variables = {variables()[: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}')
Must become this:
+ 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
To produce:
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
-
Make automated logging easier:
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!') ...
-
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.
Reference
All functions have output customization
max_value_str_len
max length of each variable stringmax_exc_str_len
max length of exception, should variable print failnum_context_lines
number of lines around the target code line to printellipsis_
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
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.
Recipes
Simplest usage
from traceback_with_variables import activate_by_import
Override standard traceback if env variable X is set
def main():
override_print_tb(activate_by_env_var='X')
Override standard traceback unless env variable Y is set
def main():
override_print_tb(deactivate_by_env_var='Y')
Log traceback for a block of code, exclude external frames
logger = logging.getLogger(__name__)
...
with printing_tb(file_=LoggerAsFile(logger)):
Log traceback for a function, exclude external frames
logger = logging.getLogger(__name__)
...
@prints_tb(file_=LoggerAsFile(logger))
def f(...):
Print traceback for inner frames
with printing_tb():
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