Get full traceback

i have written a module that writes a more complete traceback

The module is here documentation is docs

(also you can get the module from pypi

sudo pip install pd

)

To catch and pring exceptions do the following:

import pd

try:
    <python code>
except BaseException:       
    pd.print_exception_ex( follow_objects = 1 )

The stack trace looks like this one here:

Exception: got it

#1  def kuku2(self = {'a': 42, 'b': [1, 2, 3, 4]}, depth = 1) at      t  test_pd.py:29
Calls next frame at:
    raise Exception('got it') at: test_pd.py:29

#2  def kuku2(self = {'a': 42, 'b': [1, 2, 3, 4]}, depth = 2) at test_pd.py:28
Calls next frame at:
    self.kuku2( depth - 1 ) at: test_pd.py:28

#3  def kuku2(self = {'a': 42, 'b': [1, 2, 3, 4]}, depth = 3) at test_pd.py:28
Calls next frame at:
    self.kuku2( depth - 1 ) at: test_pd.py:28

#4  def kuku2(self = {'a': 42, 'b': [1, 2, 3, 4]}, depth = 4) at test_pd.py:28
Calls next frame at:
    self.kuku2( depth - 1 ) at: test_pd.py:28

#5  def kuku2(self = {'a': 42, 'b': [1, 2, 3, 4]}, depth = 5) at     test_pd.py:28
 Calls next frame at:
    self.kuku2( depth - 1 ) at: test_pd.py:28

#6  def kuku2(self = {'a': 42, 'b': [1, 2, 3, 4]}, depth = 6) at test_pd.py:28
Calls next frame at:
    self.kuku2( depth - 1 ) at: test_pd.py:28

#7  def main() at test_pd.py:44
Local variables:
n = {'a': 42, 'b': [1, 2, 3, 4]}
Calls next frame at:
    pd.print_exception_ex( follow_objects = 1 ) at: test_pd.py:44

follow_objects = 0 will not print out object content (with complex data structures follow_objects can take a lot of time).


This is based on user4815162342's answer, but a bit more minimalistic:

import sys
import collections

FauxTb = collections.namedtuple("FauxTb", ["tb_frame", "tb_lineno", "tb_next"])

def full_exc_info():
    """Like sys.exc_info, but includes the full traceback."""
    t, v, tb = sys.exc_info()
    f = sys._getframe(2)
    while f is not None:
        tb = FauxTb(f, f.f_lineno, tb)
        f = f.f_back
    return t, v, tb

It avoids throwing the dummy exception, at the cost of requiring the usage of sys._getframe(). It assumes being used in the except clause where the exception was caught, as it goes up two stack frames (full_exc_info and the function that calls full_exc_info – that would be the function that calls the raising code, and as such is already included in the original traceback).

This gives the same output as the code in user4815162342's answer.

If you don't mind the slight differences in formatting, you can also use

import logging

def func():
    try:
        raise Exception('Dummy')
    except:
        logging.exception("Something awful happened!", stack_info=True)

def func2():
    func()

func2()

which results in

ERROR:root:Something awful happened!
Traceback (most recent call last):
  File "test.py", line 5, in func
    raise Exception('Dummy')
Exception: Dummy
Stack (most recent call last):
  File "test.py", line 12, in <module>
    func2()
  File "test.py", line 10, in func2
    func()
  File "test.py", line 7, in func
    logging.exception("Something awful happened!", stack_info=True)

In this case, you'll get a trace from the try to the exception, and a second from the root call to the location of the logging call.


Stack trace is collected when exception bubbles up. So you should print traceback on top of desired stack:

import traceback

def func():
    raise Exception('Dummy')

def func2():
    func()


try:
    func2()
except:
    traceback.print_exc()

As mechmind answered, the stack trace consists only of frames between the site where the exception was raised and the site of the try block. If you need the full stack trace, apparently you're out of luck.

Except that it's obviously possible to extract the stack entries from top-level to the current frame—traceback.extract_stack manages it just fine. The problem is that the information obtained by traceback.extract_stack comes from direct inspection of stack frames without creating a traceback object at any point, and the logging API requires a traceback object to affect traceback output.

Fortunately, logging doesn't require an actual traceback object, it requires an object that it can pass to the formatting routines of the traceback module. traceback doesn't care either—it only uses two attributes of the traceback, the frame and the line number. So, it should be possible to create a linked list of duck-typed faux-traceback objects and pass it off as the traceback.

import sys

class FauxTb(object):
    def __init__(self, tb_frame, tb_lineno, tb_next):
        self.tb_frame = tb_frame
        self.tb_lineno = tb_lineno
        self.tb_next = tb_next

def current_stack(skip=0):
    try: 1/0
    except ZeroDivisionError:
        f = sys.exc_info()[2].tb_frame
    for i in xrange(skip + 2):
        f = f.f_back
    lst = []
    while f is not None:
        lst.append((f, f.f_lineno))
        f = f.f_back
    return lst

def extend_traceback(tb, stack):
    """Extend traceback with stack info."""
    head = tb
    for tb_frame, tb_lineno in stack:
        head = FauxTb(tb_frame, tb_lineno, head)
    return head

def full_exc_info():
    """Like sys.exc_info, but includes the full traceback."""
    t, v, tb = sys.exc_info()
    full_tb = extend_traceback(tb, current_stack(1))
    return t, v, full_tb

With these functions in place, your code only requires a trivial modification:

import logging

def func():
    try:
        raise Exception('Dummy')
    except:
        logging.error("Something awful happened!", exc_info=full_exc_info())

def func2():
    func()

func2()

...to give the expected output:

ERROR:root:Something awful happened!
Traceback (most recent call last):
  File "a.py", line 52, in <module>
    func2()
  File "a.py", line 49, in func2
    func()
  File "a.py", line 43, in func
    raise Exception('Dummy')
Exception: Dummy

Note that the faux-traceback objects are fully usable for introspection—displaying local variables or as argument to pdb.post_mortem()—because they contain references to real stack frames.

Tags:

Python

Traceback

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