mirror of https://github.com/python/cpython
650 lines
23 KiB
ReStructuredText
650 lines
23 KiB
ReStructuredText
:mod:`traceback` --- Print or retrieve a stack traceback
|
|
========================================================
|
|
|
|
.. module:: traceback
|
|
:synopsis: Print or retrieve a stack traceback.
|
|
|
|
**Source code:** :source:`Lib/traceback.py`
|
|
|
|
--------------
|
|
|
|
This module provides a standard interface to extract, format and print stack
|
|
traces of Python programs. It exactly mimics the behavior of the Python
|
|
interpreter when it prints a stack trace. This is useful when you want to print
|
|
stack traces under program control, such as in a "wrapper" around the
|
|
interpreter.
|
|
|
|
.. index:: pair: object; traceback
|
|
|
|
The module uses :ref:`traceback objects <traceback-objects>` --- these are
|
|
objects of type :class:`types.TracebackType`,
|
|
which are assigned to the :attr:`~BaseException.__traceback__` field of
|
|
:class:`BaseException` instances.
|
|
|
|
.. seealso::
|
|
|
|
Module :mod:`faulthandler`
|
|
Used to dump Python tracebacks explicitly, on a fault, after a timeout, or on a user signal.
|
|
|
|
Module :mod:`pdb`
|
|
Interactive source code debugger for Python programs.
|
|
|
|
The module defines the following functions:
|
|
|
|
.. function:: print_tb(tb, limit=None, file=None)
|
|
|
|
Print up to *limit* stack trace entries from
|
|
:ref:`traceback object <traceback-objects>` *tb* (starting
|
|
from the caller's frame) if *limit* is positive. Otherwise, print the last
|
|
``abs(limit)`` entries. If *limit* is omitted or ``None``, all entries are
|
|
printed. If *file* is omitted or ``None``, the output goes to
|
|
:data:`sys.stderr`; otherwise it should be an open
|
|
:term:`file <file object>` or :term:`file-like object` to
|
|
receive the output.
|
|
|
|
.. versionchanged:: 3.5
|
|
Added negative *limit* support.
|
|
|
|
|
|
.. function:: print_exception(exc, /[, value, tb], limit=None, \
|
|
file=None, chain=True)
|
|
|
|
Print exception information and stack trace entries from
|
|
:ref:`traceback object <traceback-objects>`
|
|
*tb* to *file*. This differs from :func:`print_tb` in the following
|
|
ways:
|
|
|
|
* if *tb* is not ``None``, it prints a header ``Traceback (most recent
|
|
call last):``
|
|
|
|
* it prints the exception type and *value* after the stack trace
|
|
|
|
.. index:: single: ^ (caret); marker
|
|
|
|
* if *type(value)* is :exc:`SyntaxError` and *value* has the appropriate
|
|
format, it prints the line where the syntax error occurred with a caret
|
|
indicating the approximate position of the error.
|
|
|
|
Since Python 3.10, instead of passing *value* and *tb*, an exception object
|
|
can be passed as the first argument. If *value* and *tb* are provided, the
|
|
first argument is ignored in order to provide backwards compatibility.
|
|
|
|
The optional *limit* argument has the same meaning as for :func:`print_tb`.
|
|
If *chain* is true (the default), then chained exceptions (the
|
|
:attr:`~BaseException.__cause__` or :attr:`~BaseException.__context__`
|
|
attributes of the exception) will be
|
|
printed as well, like the interpreter itself does when printing an unhandled
|
|
exception.
|
|
|
|
.. versionchanged:: 3.5
|
|
The *etype* argument is ignored and inferred from the type of *value*.
|
|
|
|
.. versionchanged:: 3.10
|
|
The *etype* parameter has been renamed to *exc* and is now
|
|
positional-only.
|
|
|
|
|
|
.. function:: print_exc(limit=None, file=None, chain=True)
|
|
|
|
This is a shorthand for ``print_exception(sys.exception(), limit, file,
|
|
chain)``.
|
|
|
|
|
|
.. function:: print_last(limit=None, file=None, chain=True)
|
|
|
|
This is a shorthand for ``print_exception(sys.last_exc, limit, file,
|
|
chain)``. In general it will work only after an exception has reached
|
|
an interactive prompt (see :data:`sys.last_exc`).
|
|
|
|
|
|
.. function:: print_stack(f=None, limit=None, file=None)
|
|
|
|
Print up to *limit* stack trace entries (starting from the invocation
|
|
point) if *limit* is positive. Otherwise, print the last ``abs(limit)``
|
|
entries. If *limit* is omitted or ``None``, all entries are printed.
|
|
The optional *f* argument can be used to specify an alternate
|
|
:ref:`stack frame <frame-objects>`
|
|
to start. The optional *file* argument has the same meaning as for
|
|
:func:`print_tb`.
|
|
|
|
.. versionchanged:: 3.5
|
|
Added negative *limit* support.
|
|
|
|
|
|
.. function:: extract_tb(tb, limit=None)
|
|
|
|
Return a :class:`StackSummary` object representing a list of "pre-processed"
|
|
stack trace entries extracted from the
|
|
:ref:`traceback object <traceback-objects>` *tb*. It is useful
|
|
for alternate formatting of stack traces. The optional *limit* argument has
|
|
the same meaning as for :func:`print_tb`. A "pre-processed" stack trace
|
|
entry is a :class:`FrameSummary` object containing attributes
|
|
:attr:`~FrameSummary.filename`, :attr:`~FrameSummary.lineno`,
|
|
:attr:`~FrameSummary.name`, and :attr:`~FrameSummary.line` representing the
|
|
information that is usually printed for a stack trace.
|
|
|
|
|
|
.. function:: extract_stack(f=None, limit=None)
|
|
|
|
Extract the raw traceback from the current
|
|
:ref:`stack frame <frame-objects>`. The return value has
|
|
the same format as for :func:`extract_tb`. The optional *f* and *limit*
|
|
arguments have the same meaning as for :func:`print_stack`.
|
|
|
|
|
|
.. function:: format_list(extracted_list)
|
|
|
|
Given a list of tuples or :class:`FrameSummary` objects as returned by
|
|
:func:`extract_tb` or :func:`extract_stack`, return a list of strings ready
|
|
for printing. Each string in the resulting list corresponds to the item with
|
|
the same index in the argument list. Each string ends in a newline; the
|
|
strings may contain internal newlines as well, for those items whose source
|
|
text line is not ``None``.
|
|
|
|
|
|
.. function:: format_exception_only(exc, /[, value], *, show_group=False)
|
|
|
|
Format the exception part of a traceback using an exception value such as
|
|
given by :data:`sys.last_value`. The return value is a list of strings, each
|
|
ending in a newline. The list contains the exception's message, which is
|
|
normally a single string; however, for :exc:`SyntaxError` exceptions, it
|
|
contains several lines that (when printed) display detailed information
|
|
about where the syntax error occurred. Following the message, the list
|
|
contains the exception's :attr:`notes <BaseException.__notes__>`.
|
|
|
|
Since Python 3.10, instead of passing *value*, an exception object
|
|
can be passed as the first argument. If *value* is provided, the first
|
|
argument is ignored in order to provide backwards compatibility.
|
|
|
|
When *show_group* is ``True``, and the exception is an instance of
|
|
:exc:`BaseExceptionGroup`, the nested exceptions are included as
|
|
well, recursively, with indentation relative to their nesting depth.
|
|
|
|
.. versionchanged:: 3.10
|
|
The *etype* parameter has been renamed to *exc* and is now
|
|
positional-only.
|
|
|
|
.. versionchanged:: 3.11
|
|
The returned list now includes any
|
|
:attr:`notes <BaseException.__notes__>` attached to the exception.
|
|
|
|
.. versionchanged:: 3.13
|
|
*show_group* parameter was added.
|
|
|
|
|
|
.. function:: format_exception(exc, /[, value, tb], limit=None, chain=True)
|
|
|
|
Format a stack trace and the exception information. The arguments have the
|
|
same meaning as the corresponding arguments to :func:`print_exception`. The
|
|
return value is a list of strings, each ending in a newline and some
|
|
containing internal newlines. When these lines are concatenated and printed,
|
|
exactly the same text is printed as does :func:`print_exception`.
|
|
|
|
.. versionchanged:: 3.5
|
|
The *etype* argument is ignored and inferred from the type of *value*.
|
|
|
|
.. versionchanged:: 3.10
|
|
This function's behavior and signature were modified to match
|
|
:func:`print_exception`.
|
|
|
|
|
|
.. function:: format_exc(limit=None, chain=True)
|
|
|
|
This is like ``print_exc(limit)`` but returns a string instead of printing to
|
|
a file.
|
|
|
|
|
|
.. function:: format_tb(tb, limit=None)
|
|
|
|
A shorthand for ``format_list(extract_tb(tb, limit))``.
|
|
|
|
|
|
.. function:: format_stack(f=None, limit=None)
|
|
|
|
A shorthand for ``format_list(extract_stack(f, limit))``.
|
|
|
|
.. function:: clear_frames(tb)
|
|
|
|
Clears the local variables of all the stack frames in a
|
|
:ref:`traceback <traceback-objects>` *tb*
|
|
by calling the :meth:`~frame.clear` method of each
|
|
:ref:`frame object <frame-objects>`.
|
|
|
|
.. versionadded:: 3.4
|
|
|
|
.. function:: walk_stack(f)
|
|
|
|
Walk a stack following :attr:`f.f_back <frame.f_back>` from the given frame,
|
|
yielding the frame
|
|
and line number for each frame. If *f* is ``None``, the current stack is
|
|
used. This helper is used with :meth:`StackSummary.extract`.
|
|
|
|
.. versionadded:: 3.5
|
|
|
|
.. function:: walk_tb(tb)
|
|
|
|
Walk a traceback following :attr:`~traceback.tb_next` yielding the frame and
|
|
line number
|
|
for each frame. This helper is used with :meth:`StackSummary.extract`.
|
|
|
|
.. versionadded:: 3.5
|
|
|
|
The module also defines the following classes:
|
|
|
|
:class:`!TracebackException` Objects
|
|
------------------------------------
|
|
|
|
.. versionadded:: 3.5
|
|
|
|
:class:`!TracebackException` objects are created from actual exceptions to
|
|
capture data for later printing in a lightweight fashion.
|
|
|
|
.. class:: TracebackException(exc_type, exc_value, exc_traceback, *, limit=None, lookup_lines=True, capture_locals=False, compact=False, max_group_width=15, max_group_depth=10)
|
|
|
|
Capture an exception for later rendering. *limit*, *lookup_lines* and
|
|
*capture_locals* are as for the :class:`StackSummary` class.
|
|
|
|
If *compact* is true, only data that is required by
|
|
:class:`!TracebackException`'s :meth:`format` method
|
|
is saved in the class attributes. In particular, the
|
|
:attr:`__context__` field is calculated only if :attr:`__cause__` is
|
|
``None`` and :attr:`__suppress_context__` is false.
|
|
|
|
Note that when locals are captured, they are also shown in the traceback.
|
|
|
|
*max_group_width* and *max_group_depth* control the formatting of exception
|
|
groups (see :exc:`BaseExceptionGroup`). The depth refers to the nesting
|
|
level of the group, and the width refers to the size of a single exception
|
|
group's exceptions array. The formatted output is truncated when either
|
|
limit is exceeded.
|
|
|
|
.. versionchanged:: 3.10
|
|
Added the *compact* parameter.
|
|
|
|
.. versionchanged:: 3.11
|
|
Added the *max_group_width* and *max_group_depth* parameters.
|
|
|
|
.. attribute:: __cause__
|
|
|
|
A :class:`!TracebackException` of the original
|
|
:attr:`~BaseException.__cause__`.
|
|
|
|
.. attribute:: __context__
|
|
|
|
A :class:`!TracebackException` of the original
|
|
:attr:`~BaseException.__context__`.
|
|
|
|
.. attribute:: exceptions
|
|
|
|
If ``self`` represents an :exc:`ExceptionGroup`, this field holds a list of
|
|
:class:`!TracebackException` instances representing the nested exceptions.
|
|
Otherwise it is ``None``.
|
|
|
|
.. versionadded:: 3.11
|
|
|
|
.. attribute:: __suppress_context__
|
|
|
|
The :attr:`~BaseException.__suppress_context__` value from the original
|
|
exception.
|
|
|
|
.. attribute:: __notes__
|
|
|
|
The :attr:`~BaseException.__notes__` value from the original exception,
|
|
or ``None``
|
|
if the exception does not have any notes. If it is not ``None``
|
|
is it formatted in the traceback after the exception string.
|
|
|
|
.. versionadded:: 3.11
|
|
|
|
.. attribute:: stack
|
|
|
|
A :class:`StackSummary` representing the traceback.
|
|
|
|
.. attribute:: exc_type
|
|
|
|
The class of the original traceback.
|
|
|
|
.. deprecated:: 3.13
|
|
|
|
.. attribute:: exc_type_str
|
|
|
|
String display of the class of the original exception.
|
|
|
|
.. versionadded:: 3.13
|
|
|
|
.. attribute:: filename
|
|
|
|
For syntax errors - the file name where the error occurred.
|
|
|
|
.. attribute:: lineno
|
|
|
|
For syntax errors - the line number where the error occurred.
|
|
|
|
.. attribute:: end_lineno
|
|
|
|
For syntax errors - the end line number where the error occurred.
|
|
Can be ``None`` if not present.
|
|
|
|
.. versionadded:: 3.10
|
|
|
|
.. attribute:: text
|
|
|
|
For syntax errors - the text where the error occurred.
|
|
|
|
.. attribute:: offset
|
|
|
|
For syntax errors - the offset into the text where the error occurred.
|
|
|
|
.. attribute:: end_offset
|
|
|
|
For syntax errors - the end offset into the text where the error occurred.
|
|
Can be ``None`` if not present.
|
|
|
|
.. versionadded:: 3.10
|
|
|
|
.. attribute:: msg
|
|
|
|
For syntax errors - the compiler error message.
|
|
|
|
.. classmethod:: from_exception(exc, *, limit=None, lookup_lines=True, capture_locals=False)
|
|
|
|
Capture an exception for later rendering. *limit*, *lookup_lines* and
|
|
*capture_locals* are as for the :class:`StackSummary` class.
|
|
|
|
Note that when locals are captured, they are also shown in the traceback.
|
|
|
|
.. method:: print(*, file=None, chain=True)
|
|
|
|
Print to *file* (default ``sys.stderr``) the exception information returned by
|
|
:meth:`format`.
|
|
|
|
.. versionadded:: 3.11
|
|
|
|
.. method:: format(*, chain=True)
|
|
|
|
Format the exception.
|
|
|
|
If *chain* is not ``True``, :attr:`__cause__` and :attr:`__context__`
|
|
will not be formatted.
|
|
|
|
The return value is a generator of strings, each ending in a newline and
|
|
some containing internal newlines. :func:`~traceback.print_exception`
|
|
is a wrapper around this method which just prints the lines to a file.
|
|
|
|
.. method:: format_exception_only(*, show_group=False)
|
|
|
|
Format the exception part of the traceback.
|
|
|
|
The return value is a generator of strings, each ending in a newline.
|
|
|
|
When *show_group* is ``False``, the generator emits the exception's
|
|
message followed by its notes (if it has any). The exception message
|
|
is normally a single string; however, for :exc:`SyntaxError` exceptions,
|
|
it consists of several lines that (when printed) display detailed
|
|
information about where the syntax error occurred.
|
|
|
|
When *show_group* is ``True``, and the exception is an instance of
|
|
:exc:`BaseExceptionGroup`, the nested exceptions are included as
|
|
well, recursively, with indentation relative to their nesting depth.
|
|
|
|
.. versionchanged:: 3.11
|
|
The exception's :attr:`notes <BaseException.__notes__>` are now
|
|
included in the output.
|
|
|
|
.. versionchanged:: 3.13
|
|
Added the *show_group* parameter.
|
|
|
|
|
|
:class:`!StackSummary` Objects
|
|
------------------------------
|
|
|
|
.. versionadded:: 3.5
|
|
|
|
:class:`!StackSummary` objects represent a call stack ready for formatting.
|
|
|
|
.. class:: StackSummary
|
|
|
|
.. classmethod:: extract(frame_gen, *, limit=None, lookup_lines=True, capture_locals=False)
|
|
|
|
Construct a :class:`!StackSummary` object from a frame generator (such as
|
|
is returned by :func:`~traceback.walk_stack` or
|
|
:func:`~traceback.walk_tb`).
|
|
|
|
If *limit* is supplied, only this many frames are taken from *frame_gen*.
|
|
If *lookup_lines* is ``False``, the returned :class:`FrameSummary`
|
|
objects will not have read their lines in yet, making the cost of
|
|
creating the :class:`!StackSummary` cheaper (which may be valuable if it
|
|
may not actually get formatted). If *capture_locals* is ``True`` the
|
|
local variables in each :class:`!FrameSummary` are captured as object
|
|
representations.
|
|
|
|
.. versionchanged:: 3.12
|
|
Exceptions raised from :func:`repr` on a local variable (when
|
|
*capture_locals* is ``True``) are no longer propagated to the caller.
|
|
|
|
.. classmethod:: from_list(a_list)
|
|
|
|
Construct a :class:`!StackSummary` object from a supplied list of
|
|
:class:`FrameSummary` objects or old-style list of tuples. Each tuple
|
|
should be a 4-tuple with *filename*, *lineno*, *name*, *line* as the
|
|
elements.
|
|
|
|
.. method:: format()
|
|
|
|
Returns a list of strings ready for printing. Each string in the
|
|
resulting list corresponds to a single :ref:`frame <frame-objects>` from
|
|
the stack.
|
|
Each string ends in a newline; the strings may contain internal
|
|
newlines as well, for those items with source text lines.
|
|
|
|
For long sequences of the same frame and line, the first few
|
|
repetitions are shown, followed by a summary line stating the exact
|
|
number of further repetitions.
|
|
|
|
.. versionchanged:: 3.6
|
|
Long sequences of repeated frames are now abbreviated.
|
|
|
|
.. method:: format_frame_summary(frame_summary)
|
|
|
|
Returns a string for printing one of the :ref:`frames <frame-objects>`
|
|
involved in the stack.
|
|
This method is called for each :class:`FrameSummary` object to be
|
|
printed by :meth:`StackSummary.format`. If it returns ``None``, the
|
|
frame is omitted from the output.
|
|
|
|
.. versionadded:: 3.11
|
|
|
|
|
|
:class:`!FrameSummary` Objects
|
|
------------------------------
|
|
|
|
.. versionadded:: 3.5
|
|
|
|
A :class:`!FrameSummary` object represents a single :ref:`frame <frame-objects>`
|
|
in a :ref:`traceback <traceback-objects>`.
|
|
|
|
.. class:: FrameSummary(filename, lineno, name, lookup_line=True, locals=None, line=None)
|
|
|
|
Represents a single :ref:`frame <frame-objects>` in the
|
|
:ref:`traceback <traceback-objects>` or stack that is being formatted
|
|
or printed. It may optionally have a stringified version of the frame's
|
|
locals included in it. If *lookup_line* is ``False``, the source code is not
|
|
looked up until the :class:`!FrameSummary` has the :attr:`~FrameSummary.line`
|
|
attribute accessed (which also happens when casting it to a :class:`tuple`).
|
|
:attr:`~FrameSummary.line` may be directly provided, and will prevent line
|
|
lookups happening at all. *locals* is an optional local variable
|
|
dictionary, and if supplied the variable representations are stored in the
|
|
summary for later display.
|
|
|
|
:class:`!FrameSummary` instances have the following attributes:
|
|
|
|
.. attribute:: FrameSummary.filename
|
|
|
|
The filename of the source code for this frame. Equivalent to accessing
|
|
:attr:`f.f_code.co_filename <codeobject.co_filename>` on a
|
|
:ref:`frame object <frame-objects>` *f*.
|
|
|
|
.. attribute:: FrameSummary.lineno
|
|
|
|
The line number of the source code for this frame.
|
|
|
|
.. attribute:: FrameSummary.name
|
|
|
|
Equivalent to accessing :attr:`f.f_code.co_name <codeobject.co_name>` on
|
|
a :ref:`frame object <frame-objects>` *f*.
|
|
|
|
.. attribute:: FrameSummary.line
|
|
|
|
A string representing the source code for this frame, with leading and
|
|
trailing whitespace stripped.
|
|
If the source is not available, it is ``None``.
|
|
|
|
.. _traceback-example:
|
|
|
|
Traceback Examples
|
|
------------------
|
|
|
|
This simple example implements a basic read-eval-print loop, similar to (but
|
|
less useful than) the standard Python interactive interpreter loop. For a more
|
|
complete implementation of the interpreter loop, refer to the :mod:`code`
|
|
module. ::
|
|
|
|
import sys, traceback
|
|
|
|
def run_user_code(envdir):
|
|
source = input(">>> ")
|
|
try:
|
|
exec(source, envdir)
|
|
except Exception:
|
|
print("Exception in user code:")
|
|
print("-"*60)
|
|
traceback.print_exc(file=sys.stdout)
|
|
print("-"*60)
|
|
|
|
envdir = {}
|
|
while True:
|
|
run_user_code(envdir)
|
|
|
|
|
|
The following example demonstrates the different ways to print and format the
|
|
exception and traceback:
|
|
|
|
.. testcode::
|
|
|
|
import sys, traceback
|
|
|
|
def lumberjack():
|
|
bright_side_of_life()
|
|
|
|
def bright_side_of_life():
|
|
return tuple()[0]
|
|
|
|
try:
|
|
lumberjack()
|
|
except IndexError:
|
|
exc = sys.exception()
|
|
print("*** print_tb:")
|
|
traceback.print_tb(exc.__traceback__, limit=1, file=sys.stdout)
|
|
print("*** print_exception:")
|
|
traceback.print_exception(exc, limit=2, file=sys.stdout)
|
|
print("*** print_exc:")
|
|
traceback.print_exc(limit=2, file=sys.stdout)
|
|
print("*** format_exc, first and last line:")
|
|
formatted_lines = traceback.format_exc().splitlines()
|
|
print(formatted_lines[0])
|
|
print(formatted_lines[-1])
|
|
print("*** format_exception:")
|
|
print(repr(traceback.format_exception(exc)))
|
|
print("*** extract_tb:")
|
|
print(repr(traceback.extract_tb(exc.__traceback__)))
|
|
print("*** format_tb:")
|
|
print(repr(traceback.format_tb(exc.__traceback__)))
|
|
print("*** tb_lineno:", exc.__traceback__.tb_lineno)
|
|
|
|
The output for the example would look similar to this:
|
|
|
|
.. testoutput::
|
|
:options: +NORMALIZE_WHITESPACE
|
|
|
|
*** print_tb:
|
|
File "<doctest...>", line 10, in <module>
|
|
lumberjack()
|
|
~~~~~~~~~~^^
|
|
*** print_exception:
|
|
Traceback (most recent call last):
|
|
File "<doctest...>", line 10, in <module>
|
|
lumberjack()
|
|
~~~~~~~~~~^^
|
|
File "<doctest...>", line 4, in lumberjack
|
|
bright_side_of_life()
|
|
~~~~~~~~~~~~~~~~~~~^^
|
|
IndexError: tuple index out of range
|
|
*** print_exc:
|
|
Traceback (most recent call last):
|
|
File "<doctest...>", line 10, in <module>
|
|
lumberjack()
|
|
~~~~~~~~~~^^
|
|
File "<doctest...>", line 4, in lumberjack
|
|
bright_side_of_life()
|
|
~~~~~~~~~~~~~~~~~~~^^
|
|
IndexError: tuple index out of range
|
|
*** format_exc, first and last line:
|
|
Traceback (most recent call last):
|
|
IndexError: tuple index out of range
|
|
*** format_exception:
|
|
['Traceback (most recent call last):\n',
|
|
' File "<doctest default[0]>", line 10, in <module>\n lumberjack()\n ~~~~~~~~~~^^\n',
|
|
' File "<doctest default[0]>", line 4, in lumberjack\n bright_side_of_life()\n ~~~~~~~~~~~~~~~~~~~^^\n',
|
|
' File "<doctest default[0]>", line 7, in bright_side_of_life\n return tuple()[0]\n ~~~~~~~^^^\n',
|
|
'IndexError: tuple index out of range\n']
|
|
*** extract_tb:
|
|
[<FrameSummary file <doctest...>, line 10 in <module>>,
|
|
<FrameSummary file <doctest...>, line 4 in lumberjack>,
|
|
<FrameSummary file <doctest...>, line 7 in bright_side_of_life>]
|
|
*** format_tb:
|
|
[' File "<doctest default[0]>", line 10, in <module>\n lumberjack()\n ~~~~~~~~~~^^\n',
|
|
' File "<doctest default[0]>", line 4, in lumberjack\n bright_side_of_life()\n ~~~~~~~~~~~~~~~~~~~^^\n',
|
|
' File "<doctest default[0]>", line 7, in bright_side_of_life\n return tuple()[0]\n ~~~~~~~^^^\n']
|
|
*** tb_lineno: 10
|
|
|
|
|
|
The following example shows the different ways to print and format the stack::
|
|
|
|
>>> import traceback
|
|
>>> def another_function():
|
|
... lumberstack()
|
|
...
|
|
>>> def lumberstack():
|
|
... traceback.print_stack()
|
|
... print(repr(traceback.extract_stack()))
|
|
... print(repr(traceback.format_stack()))
|
|
...
|
|
>>> another_function()
|
|
File "<doctest>", line 10, in <module>
|
|
another_function()
|
|
File "<doctest>", line 3, in another_function
|
|
lumberstack()
|
|
File "<doctest>", line 6, in lumberstack
|
|
traceback.print_stack()
|
|
[('<doctest>', 10, '<module>', 'another_function()'),
|
|
('<doctest>', 3, 'another_function', 'lumberstack()'),
|
|
('<doctest>', 7, 'lumberstack', 'print(repr(traceback.extract_stack()))')]
|
|
[' File "<doctest>", line 10, in <module>\n another_function()\n',
|
|
' File "<doctest>", line 3, in another_function\n lumberstack()\n',
|
|
' File "<doctest>", line 8, in lumberstack\n print(repr(traceback.format_stack()))\n']
|
|
|
|
|
|
This last example demonstrates the final few formatting functions:
|
|
|
|
.. doctest::
|
|
:options: +NORMALIZE_WHITESPACE
|
|
|
|
>>> import traceback
|
|
>>> traceback.format_list([('spam.py', 3, '<module>', 'spam.eggs()'),
|
|
... ('eggs.py', 42, 'eggs', 'return "bacon"')])
|
|
[' File "spam.py", line 3, in <module>\n spam.eggs()\n',
|
|
' File "eggs.py", line 42, in eggs\n return "bacon"\n']
|
|
>>> an_error = IndexError('tuple index out of range')
|
|
>>> traceback.format_exception_only(type(an_error), an_error)
|
|
['IndexError: tuple index out of range\n']
|