How to Print a Stack Trace in Python (traceback Module)

The simplest way to print a stack trace in Python without crashing is traceback.print_exc() inside an except block. It prints the full traceback, exactly as an uncaught error would, and your program keeps running:

import traceback

try:
    risky()
except Exception:
    traceback.print_exc()

Each traceback below is real output from Python 3.12.5, captured in Windows Command Prompt.

I’ll show print_exc(), getting the trace as a string, formatting a saved exception, logging it properly, printing the current stack without an error, and chained exceptions.

How to print a stack trace with traceback.print_exc()

print_exc() reads the exception currently being handled and writes its traceback to standard error. Here a bad price string fails two calls deep:

import traceback

def load_price(row):
    return float(row["price"])

def total(rows):
    return sum(load_price(r) for r in rows)

orders = [{"price": "19.99"}, {"price": "N/A"}]
try:
    print(total(orders))
except ValueError:
    traceback.print_exc()             # full traceback, and the program keeps going
print("still running")

Output:

Traceback (most recent call last):
  File "C:\pyguides\trace_print_exc.py", line 11, in <module>
    print(total(orders))
          ^^^^^^^^^^^^^
  File "C:\pyguides\trace_print_exc.py", line 7, in total
    return sum(load_price(r) for r in rows)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\pyguides\trace_print_exc.py", line 7, in <genexpr>
    return sum(load_price(r) for r in rows)
               ^^^^^^^^^^^^^
  File "C:\pyguides\trace_print_exc.py", line 4, in load_price
    return float(row["price"])
           ^^^^^^^^^^^^^^^^^^^
ValueError: could not convert string to float: 'N/A'
still running

Read it bottom-up: the last line is the error, and the frames above show how you got there. Types of errors in Python walks through reading tracebacks in more detail.

Getting the traceback as a string with format_exc()

traceback.format_exc() returns the same text instead of printing it. That’s what you want for emails, error reports or a database column:

import traceback

try:
    {"TX": 0.0625}["NY"]
except KeyError:
    details = traceback.format_exc()  # the same text, as a string

print(type(details).__name__, len(details.splitlines()), "lines")
print(details.splitlines()[-1])        # just the last line

Output:

str 5 lines
KeyError: 'NY'

Grab just the last line when you only need a short summary, like in a status message.

How do you print the traceback from an exception object?

Sometimes you have the exception saved in a variable and want its trace later. Since Python 3.10, traceback.format_exception() accepts the exception by itself:

import traceback

def parse_qty(text):
    return int(text)

try:
    parse_qty("two")
except ValueError as err:
    lines = traceback.format_exception(err)          # Python 3.10+: pass just the exception
    print("".join(lines), end="")
    frame = traceback.extract_tb(err.__traceback__)[-1]
    print(f"failed in {frame.name}() on line {frame.lineno}")

Output:

Traceback (most recent call last):
  File "C:\pyguides\trace_exception.py", line 7, in <module>
    parse_qty("two")
  File "C:\pyguides\trace_exception.py", line 4, in parse_qty
    return int(text)
           ^^^^^^^^^
ValueError: invalid literal for int() with base 10: 'two'
failed in parse_qty() on line 4

extract_tb() turns the traceback into frame objects, so you can pull out the function name, file and line number programmatically.

Logging a stack trace with logging.exception()

In real applications I send tracebacks to the logs rather than the console. log.exception() logs at ERROR level and appends the traceback automatically:

import logging

logging.basicConfig(format="%(levelname)s %(name)s: %(message)s", level=logging.INFO)
log = logging.getLogger("orders")

def charge(amount):
    if amount <= 0:
        raise ValueError(f"invalid amount ${amount:.2f}")
    return f"charged ${amount:.2f}"

for amount in (24.99, 0):
    try:
        log.info(charge(amount))
    except ValueError:
        log.exception("charge failed")   # logs at ERROR level with the traceback

Output:

INFO orders: charged $24.99
ERROR orders: charge failed
Traceback (most recent call last):
  File "C:\pyguides\trace_logging.py", line 13, in <module>
    log.info(charge(amount))
             ^^^^^^^^^^^^^^
  File "C:\pyguides\trace_logging.py", line 8, in charge
    raise ValueError(f"invalid amount ${amount:.2f}")
ValueError: invalid amount $0.00

Don’t call it outside an except block. For other levels, pass exc_info=True, such as log.warning("retrying", exc_info=True). More on handling errors in catching multiple exceptions.

Printing the current call stack without an exception

traceback.print_stack() shows how the code reached the current line, even when nothing went wrong. I use it to track down who keeps calling a function:

import traceback

def audit():
    traceback.print_stack(limit=3)       # where are we? no exception needed

def place_order():
    audit()

def checkout():
    place_order()

checkout()

Output:

  File "C:\pyguides\trace_print_stack.py", line 10, in checkout
    place_order()
  File "C:\pyguides\trace_print_stack.py", line 7, in place_order
    audit()
  File "C:\pyguides\trace_print_stack.py", line 4, in audit
    traceback.print_stack(limit=3)       # where are we? no exception needed

Stack traces for chained exceptions

When you’re raising a new exception while handling another, use raise ... from err. The traceback then shows both, so the original cause isn’t lost:

import traceback

def read_config(path):
    try:
        open(path)
    except FileNotFoundError as err:
        raise RuntimeError("config is missing") from err

try:
    read_config("settings_2026.ini")
except RuntimeError:
    traceback.print_exc()

Output:

Traceback (most recent call last):
  File "C:\pyguides\trace_chain.py", line 5, in read_config
    open(path)
FileNotFoundError: [Errno 2] No such file or directory: 'settings_2026.ini'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\pyguides\trace_chain.py", line 10, in <module>
    read_config("settings_2026.ini")
  File "C:\pyguides\trace_chain.py", line 7, in read_config
    raise RuntimeError("config is missing") from err
RuntimeError: config is missing

Which traceback function to use

Function	What it does
traceback.print_exc()	Print the current exception’s traceback to stderr
traceback.format_exc()	Return it as a string
traceback.format_exception(err)	Format a saved exception (list of strings)
logging.exception(msg)	Log at ERROR level with the traceback
traceback.print_stack()	Print the current call stack, no exception needed

These pair well with stack traces:

• Exception handling in Python
• UnboundLocalError in Python
• ModuleNotFoundError after pip install
• Python with open() as file

Frequently asked questions