`traceback`

The Python traceback module provides utilities for working with error tracebacks in Python programs. It’s particularly useful for debugging and error handling, as it allows you to capture and display the call stack of a program when an exception occurs.

Here’s a quick example:

>>> import traceback

>>> try:
...     {"a": 1}["b"]
... except KeyError:
...     traceback.print_exc()
Traceback (most recent call last):
    ...
KeyError: 'b'

Key Features

Extracts stack traces from traceback objects
Formats stack traces for display
Prints exceptions and their stack traces to standard error
Supports customization of traceback formatting
Captures complete exception information for debugging and logging
Works with both caught and uncaught exceptions

Frequently Used Classes and Functions

Object	Type	Description
`traceback.format_exc()`	Function	Returns a string representation of the current exception
`traceback.print_exc()`	Function	Prints the current exception to `sys.stderr`
`traceback.extract_tb()`	Function	Extracts and returns a list of traceback frames
`traceback.format_tb()`	Function	Formats a list of traceback frames as strings
`traceback.format_list()`	Function	Formats a list of traceback frames as string

Examples

Formats and prints the current exception’s stack trace:

>>> import traceback

>>> try:
...     int("abc")
... except ValueError:
...     print(traceback.format_exc())
Traceback (most recent call last):
    ...
ValueError: invalid literal for int() with base 10: 'abc'

Extracts and formats traceback information:

>>> lst = []

>>> try:
...     lst[1]
... except IndexError as e:
...     tb = traceback.extract_tb(e.__traceback__)
...     print(traceback.format_list(tb))
['  File "<stdin>", line 3, in <module>\n']

Common Use Cases

Capturing and logging error stack traces for debugging
Displaying detailed error messages to users
Analyzing exceptions in a post-mortem debugging scenario
Writing exception details to log files for later review
Integrating with error monitoring or reporting systems

Real-World Example

Say that you need to read a file and handle errors gracefully if the file is missing. The traceback module can be used to capture and log detailed information about such exceptions:

>>> import traceback

>>> try:
...     # Open a non-existing file
...     with open("file.txt", mode="r", encoding="utf-8") as file:
...         content = file.read()
... except FileNotFoundError as e:
...     with open("error.log", "w") as log_file:
...         log_file.write(traceback.format_exc())
...

By writing the stack trace to error.log, you ensure that detailed error information is available for future review—making debugging and troubleshooting much easier.

This technique provides a reliable way to capture detailed error information for later debugging and troubleshooting.

traceback