Prints the entire warning stack when a warning is raised by a called function

warnings_with_stacktrace.py

'''
This sample script emits the entire warning stacktrace like the following:


$ python3 -m warnings_with_stacktrace
2025-07-12 01:18:09 WARNING [warnings_with_stacktrace.py:76] Caught DeprecationWarning: This function is deprecated
File: /home/kyle/tmp/py_sandbox/warnings_with_stacktrace.py, line 36
Full stack:
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/kyle/tmp/py_sandbox/warnings_with_stacktrace.py", line 90, in <module>
    main()
  File "/home/kyle/tmp/py_sandbox/warnings_with_stacktrace.py", line 86, in main
    print(deprecated_function())
  File "/home/kyle/tmp/py_sandbox/warnings_with_stacktrace.py", line 36, in deprecated_function
    warnings.warn('This function is deprecated', DeprecationWarning)

5
'''

import logging
import os
import sys
import traceback
import warnings

logging.basicConfig(
    format='%(asctime)s %(levelname)s [%(filename)s:%(lineno)d] %(message)s',
    datefmt='%Y-%m-%d %H:%M:%S',
)
logging.captureWarnings(True)
LOGGER = logging.getLogger(__name__)
LOGGER.setLevel(logging.WARN)


def deprecated_function():
    warnings.warn('This function is deprecated', DeprecationWarning)
    return 5


def custom_showwarning(
        message,
        category,
        filename,
        lineno,
        file=None,  # file outputted to
        line=None,  # source code of line that issued the warning
):
    # Get full stack
    stack = traceback.extract_stack()

    LOGGER.debug('Handling warning for %s:%s', filename, lineno)
    # Normalize filename to absolute path for consistent comparison
    abs_filename = os.path.abspath(filename)

    # Find the last frame that matches the filename and line number
    cutoff_index = None
    for i, frame in enumerate(stack):
        LOGGER.debug('Frame %s: %s:%s', i, frame.filename, frame.lineno)
        if os.path.abspath(
                frame.filename) == abs_filename and frame.lineno == lineno:
            cutoff_index = i
            break

    if cutoff_index is not None:
        cleaned_stack = stack[:cutoff_index + 1]
    else:
        # Fall back if we don't find a match
        cleaned_stack = stack

    formatted_stack = ''.join(traceback.format_list(cleaned_stack))

    # log_message = 'jim'
    log_message = (f'Caught {category.__name__}: {message}\n'
                   f'File: {filename}, line {lineno}\n'
                   f'Full stack:\n{formatted_stack}')
    LOGGER.warning(log_message)


# Replace the default showwarning with yours
if not sys.warnoptions:
    warnings.simplefilter('once')
warnings.showwarning = custom_showwarning


def main():
    print(deprecated_function())


if __name__ == '__main__':
    main()