From f47a40034763e9877861d995402715ca0dedb17c Mon Sep 17 00:00:00 2001 From: Martin Panter Date: Sun, 15 May 2016 00:13:04 +0000 Subject: Issue #25533: Update documentation regarding the frozen modules table * "ctypes" documentation was using Python 2 bytes-str equivalence. * PyImport_FrozenModules is a pointer to const as of Python 3.4 --- Doc/c-api/import.rst | 2 +- Doc/library/ctypes.rst | 11 ++++++----- Doc/library/pkgutil.rst | 4 ++-- Lib/ctypes/test/test_values.py | 11 ++++++----- 4 files changed, 15 insertions(+), 13 deletions(-) diff --git a/Doc/c-api/import.rst b/Doc/c-api/import.rst index 86c1d7d..2936f4f 100644 --- a/Doc/c-api/import.rst +++ b/Doc/c-api/import.rst @@ -272,7 +272,7 @@ Importing Modules }; -.. c:var:: struct _frozen* PyImport_FrozenModules +.. c:var:: const struct _frozen* PyImport_FrozenModules This pointer is initialized to point to an array of :c:type:`struct _frozen` records, terminated by one whose members are all *NULL* or zero. When a frozen diff --git a/Doc/library/ctypes.rst b/Doc/library/ctypes.rst index 4da276c..1d45a37 100644 --- a/Doc/library/ctypes.rst +++ b/Doc/library/ctypes.rst @@ -1100,14 +1100,15 @@ access violation or whatever, so it's better to break out of the loop when we hit the NULL entry:: >>> for item in table: - ... print(item.name, item.size) ... if item.name is None: ... break + ... print(item.name.decode("ascii"), item.size) ... - __hello__ 104 - __phello__ -104 - __phello__.spam 104 - None 0 + _frozen_importlib 31764 + _frozen_importlib_external 41499 + __hello__ 161 + __phello__ -161 + __phello__.spam 161 >>> The fact that standard Python has a frozen module and a frozen package diff --git a/Doc/library/pkgutil.rst b/Doc/library/pkgutil.rst index 5d3295d..26c5ac0 100644 --- a/Doc/library/pkgutil.rst +++ b/Doc/library/pkgutil.rst @@ -140,7 +140,7 @@ support. .. function:: iter_modules(path=None, prefix='') Yields ``(module_finder, name, ispkg)`` for all submodules on *path*, or, if - path is ``None``, all top-level modules on ``sys.path``. + *path* is ``None``, all top-level modules on ``sys.path``. *path* should be either ``None`` or a list of paths to look for modules in. @@ -161,7 +161,7 @@ support. .. function:: walk_packages(path=None, prefix='', onerror=None) Yields ``(module_finder, name, ispkg)`` for all modules recursively on - *path*, or, if path is ``None``, all accessible modules. + *path*, or, if *path* is ``None``, all accessible modules. *path* should be either ``None`` or a list of paths to look for modules in. diff --git a/Lib/ctypes/test/test_values.py b/Lib/ctypes/test/test_values.py index c7c78ce..5a3a47f 100644 --- a/Lib/ctypes/test/test_values.py +++ b/Lib/ctypes/test/test_values.py @@ -77,13 +77,14 @@ class PythonValuesTestCase(unittest.TestCase): self.assertTrue(entry.size, "{!r} was reported as having no size".format(entry.name)) continue - items.append((entry.name, entry.size)) + items.append((entry.name.decode("ascii"), entry.size)) - expected = [(b"__hello__", 161), - (b"__phello__", -161), - (b"__phello__.spam", 161), + expected = [("__hello__", 161), + ("__phello__", -161), + ("__phello__.spam", 161), ] - self.assertEqual(items, expected) + self.assertEqual(items, expected, "PyImport_FrozenModules example " + "in Doc/library/ctypes.rst may be out of date") self.assertEqual(sorted(bootstrap_seen), bootstrap_expected, "frozen bootstrap modules did not match PyImport_FrozenModules") -- cgit v0.12 8 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 
: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:: object: traceback

The module uses traceback objects --- this is the object type that is stored in
the :data:`sys.last_traceback` variable and returned as the third item from
:func:`sys.exc_info`.

The module defines the following functions:


.. function:: print_tb(tb, limit=None, file=None)

   Print up to *limit* stack trace entries from traceback object *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
   ``sys.stderr``; otherwise it should be an open file or file-like object to
   receive the output.

   .. versionchanged:: 3.5
       Added negative *limit* support.


.. function:: print_exception(etype, value, tb, limit=None, file=None, chain=True)

   Print exception information and stack trace entries from traceback object
   *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 *etype* 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.

   The optional *limit* argument has the same meaning as for :func:`print_tb`.
   If *chain* is true (the default), then chained exceptions (the
   :attr:`__cause__` or :attr:`__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*.


.. function:: print_exc(limit=None, file=None, chain=True)

   This is a shorthand for ``print_exception(*sys.exc_info(), limit, file,
   chain)``.


.. function:: print_last(limit=None, file=None, chain=True)

   This is a shorthand for ``print_exception(sys.last_type, sys.last_value,
   sys.last_traceback, limit, file, chain)``.  In general it will work only
   after an exception has reached an interactive prompt (see
   :data:`sys.last_type`).


.. 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 stack frame
   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 traceback object *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.  The
   :attr:`~FrameSummary.line` is a string with leading and trailing
   whitespace stripped; if the source is not available it is ``None``.


.. function:: extract_stack(f=None, limit=None)

   Extract the raw traceback from the current stack frame.  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(etype, value)

   Format the exception part of a traceback.  The arguments are the exception
   type and value such as given by ``sys.last_type`` and ``sys.last_value``.
   The return value is a list of strings, each ending in a newline.  Normally,
   the list contains a single string; however, for :exc:`SyntaxError`
   exceptions, it contains several lines that (when printed) display detailed
   information about where the syntax error occurred.  The message indicating
   which exception occurred is the always last string in the list.


.. function:: format_exception(etype, 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*.


.. 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 traceback *tb*
   by calling the :meth:`clear` method of each frame object.

   .. versionadded:: 3.4

.. function:: walk_stack(f)

   Walk a stack following ``f.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 ``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)

   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.

   .. attribute:: __cause__

      A :class:`TracebackException` of the original ``__cause__``.

   .. attribute:: __context__

      A :class:`TracebackException` of the original ``__context__``.

   .. attribute:: __suppress_context__

      The ``__suppress_context__`` value from the original exception.

   .. attribute:: stack

      A :class:`StackSummary` representing the traceback.

   .. attribute:: exc_type

      The class of the original traceback.

   .. 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:: 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:: 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:: format(*, chain=True)

      Format the exception.

      If *chain* is not ``True``, ``__cause__`` and ``__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.

      The message indicating which exception occurred is always the last
      string in the output.

   .. method::  format_exception_only()

      Format the exception part of the traceback.

      The return value is a generator of strings, each ending in a newline.

      Normally, the generator emits a single string; however, for
      :exc:`SyntaxError` exceptions, it emits several lines that (when
      printed) display detailed information about where the syntax
      error occurred.

      The message indicating which exception occurred is always the last
      string in the output.


: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.

   .. 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 frame 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.


:class:`FrameSummary` Objects
-----------------------------

.. versionadded:: 3.5

:class:`FrameSummary` objects represent a single frame in a traceback.

.. class:: FrameSummary(filename, lineno, name, lookup_line=True, locals=None, line=None)

   Represent a single frame in the traceback or stack that is being formatted
   or printed. It may optionally have a stringified version of the frames
   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 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.

.. _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_death()

   def bright_side_of_death():
       return tuple()[0]

   try:
       lumberjack()
   except IndexError:
       exc_type, exc_value, exc_traceback = sys.exc_info()
       print("*** print_tb:")
       traceback.print_tb(exc_traceback, limit=1, file=sys.stdout)
       print("*** print_exception:")
       # exc_type below is ignored on 3.5 and later
       traceback.print_exception(exc_type, exc_value, exc_traceback,
                                 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:")
       # exc_type below is ignored on 3.5 and later
       print(repr(traceback.format_exception(exc_type, exc_value,
                                             exc_traceback)))
       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_death()
   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_death()
   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...>", line 10, in <module>\n    lumberjack()\n',
    '  File "<doctest...>", line 4, in lumberjack\n    bright_side_of_death()\n',
    '  File "<doctest...>", line 7, in bright_side_of_death\n    return tuple()[0]\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_death>]
   *** format_tb:
   ['  File "<doctest...>", line 10, in <module>\n    lumberjack()\n',
    '  File "<doctest...>", line 4, in lumberjack\n    bright_side_of_death()\n',
    '  File "<doctest...>", line 7, in bright_side_of_death\n    return tuple()[0]\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']
generated by cgit v0.12 at 2025-09-29 06:36:08 (GMT)