Print current call stack from a method in code

Question

In Python, how can I print the current call stack from within a method (for debugging purposes).

Quentin Pradet · Accepted Answer · 2015-10-26 07:34:26Z

550

Here's an example of getting the stack via the traceback module, and printing it:

import traceback

def f():
    g()

def g():
    for line in traceback.format_stack():
        print(line.strip())

f()

# Prints:
# File "so-stack.py", line 10, in <module>
#     f()
# File "so-stack.py", line 4, in f
#     g()
# File "so-stack.py", line 7, in g
#     for line in traceback.format_stack():

If you really only want to print the stack to stderr, you can use:

traceback.print_stack()

Or to print to stdout (useful if want to keep redirected output together), use:

traceback.print_stack(file=sys.stdout)

But getting it via traceback.format_stack() lets you do whatever you like with it.

edited Oct 26, 2015 at 7:34

Quentin Pradet

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answered Jul 20, 2009 at 21:27

RichieHindle

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8 Comments

user2284570 Over a year ago

How to do the same for all other threads (I’m talking about threads I don’t control) ?

Chris Over a year ago

Maybe I'm missing something here, but you call f which it's only purpose is here is to call g and does nothing else. Why

RichieHindle Over a year ago

@Chris: It's just an example. It has multiple functions to make it clear that format_stack() prints all the calls on the stack.

Albert Over a year ago

If you want to get some more verbose output (including vars etc), see this related question, and this one.

Albert Over a year ago

@user2284570: You can use sys._current_frames(). E.g. py_better_exchook dump_all_thread_tracebacks does that (disclaimer: I wrote that).

|

Mark Roddy · Accepted Answer · 2009-07-20 21:28:14Z

169

import traceback
traceback.print_stack()

answered Jul 20, 2009 at 21:28

Mark Roddy

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3 Comments

martineau Over a year ago

Actually, I like traceback.print_exc() which gives you almost the same thing you would have gotten without the except statement (and is also less coding than the accepted answer).

Tom Swirly Over a year ago

traceback.print_exc() prints the stack trace for any exception that you might be handling - but this does not solve the original question, which is how to print the current stack ("where you are now" as opposed to "where your code was when the last exception went off, if any".)

Davy Over a year ago

It may be useful to limit the trace to a number of entries, e.g.: traceback.print_stack(limit=4)

mouserat · Accepted Answer · 2020-01-24 10:41:59Z

131

for those who need to print the call stack while using pdb, just do

(Pdb) where

answered Jan 24, 2020 at 10:41

mouserat

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Comments

Fred Loney · Accepted Answer · 2013-04-24 19:37:20Z

90

inspect.stack() returns the current stack rather than the exception traceback:

import inspect
print inspect.stack()

See https://gist.github.com/FredLoney/5454553 for a log_stack utility function.

answered Apr 24, 2013 at 19:37

Fred Loney

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1 Comment

GhostCat Over a year ago

Should have much more votes, inspect feels way better to use.

Keir · Accepted Answer · 2016-10-23 20:47:36Z

24

If you use python debugger, not only interactive probing of variables but you can get the call stack with the "where" command or "w".

So at the top of your program

import pdb

Then in the code where you want to see what is happening

pdb.set_trace()

and you get dropped into a prompt

answered Oct 23, 2016 at 20:47

Keir

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5 Comments

hosford42 Over a year ago

I've been programming in Python for over a decade. There are so many times I could have used this! I can't believe I'm just now finding out about it.

nikodaemus Over a year ago

How does this relate to where?

stephenmm Over a year ago

To answer the "where" part of the question: After you get the pdb prompt (pdb) just type where and it will print the stack trace to the terminal.

user650654 Over a year ago

Python 3.7 and above have a builtin function breakpoint() which obviates the need to import pdb.

Sherman Over a year ago

A note for anyone who tries this out in a jupyter notebook: enter exit() into the prompt to get the cell to finish executing.

martineau · Accepted Answer · 2018-02-06 22:42:54Z

8

Here's a variation of @RichieHindle's excellent answer which implements a decorator that can be selectively applied to functions as desired. Works with Python 2.7.14 and 3.6.4.

from __future__ import print_function
import functools
import traceback
import sys

INDENT = 4*' '

def stacktrace(func):
    @functools.wraps(func)
    def wrapped(*args, **kwds):
        # Get all but last line returned by traceback.format_stack()
        # which is the line below.
        callstack = '\n'.join([INDENT+line.strip() for line in traceback.format_stack()][:-1])
        print('{}() called:'.format(func.__name__))
        print(callstack)
        return func(*args, **kwds)

    return wrapped

@stacktrace
def test_func():
    return 42

print(test_func())

Output from sample:

test_func() called:
    File "stacktrace_decorator.py", line 28, in <module>
    print(test_func())
42

answered Feb 6, 2018 at 22:42

martineau

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1 Comment

Sida Zhou Over a year ago

Wrote my own decorator version before I saw this. Upvoted.

Vitalizzare · Accepted Answer · 2024-07-07 05:44:29Z

4

Install Inspect-it

pip3 install inspect-it --user

Code

import inspect
print(*['{:40}| {}:{}\n'.format(x.function, x.filename, x.lineno) 
        for x in inspect.stack()])

you can Make a snippet of this line

it will show you a list of the function call stack with a filename and line number

list from start to where you put this line

edited Jul 7, 2024 at 5:44

Vitalizzare

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answered Jul 5, 2019 at 5:49

MohitGhodasara

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1 Comment

bfontaine Dec 17, 2024 at 17:10

Why do you need to install a module? inspect.stack() is in the standard library

Arseniy Alekseyev · Accepted Answer · 2024-08-28 10:13:35Z

1

A self-contained expression that you can paste into code you're trying to debug without having to adjust the imports:

__import__("traceback").print_stack(file=__import__("sys").stderr)

answered Aug 28, 2024 at 10:13

Arseniy Alekseyev

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Comments

storenth · Accepted Answer · 2024-02-12 13:52:27Z

0

Use walk_stack method to return to the history stored in the current stack (None):

import traceback
for trace, _ in traceback.walk_stack(None):
    print(trace)
    print(trace.f_locals)

answered Feb 12, 2024 at 13:52

storenth

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