# -*- coding: utf-8 -*- """ Pdb debugger class. This is an extension to PDB which adds a number of new features. Note that there is also the `IPython.terminal.debugger` class which provides UI improvements. We also strongly recommend to use this via the `ipdb` package, which provides extra configuration options. Among other things, this subclass of PDB: - supports many IPython magics like pdef/psource - hide frames in tracebacks based on `__tracebackhide__` - allows to skip frames based on `__debuggerskip__` The skipping and hiding frames are configurable via the `skip_predicates` command. By default, frames from readonly files will be hidden, frames containing ``__tracebackhide__=True`` will be hidden. Frames containing ``__debuggerskip__`` will be stepped over, frames who's parent frames value of ``__debuggerskip__`` is ``True`` will be skipped. >>> def helpers_helper(): ... pass ... ... def helper_1(): ... print("don't step in me") ... helpers_helpers() # will be stepped over unless breakpoint set. ... ... ... def helper_2(): ... print("in me neither") ... One can define a decorator that wraps a function between the two helpers: >>> def pdb_skipped_decorator(function): ... ... ... def wrapped_fn(*args, **kwargs): ... __debuggerskip__ = True ... helper_1() ... __debuggerskip__ = False ... result = function(*args, **kwargs) ... __debuggerskip__ = True ... helper_2() ... # setting __debuggerskip__ to False again is not necessary ... return result ... ... return wrapped_fn When decorating a function, ipdb will directly step into ``bar()`` by default: >>> @foo_decorator ... def bar(x, y): ... return x * y You can toggle the behavior with ipdb> skip_predicates debuggerskip false or configure it in your ``.pdbrc`` License ------- Modified from the standard pdb.Pdb class to avoid including readline, so that the command line completion of other programs which include this isn't damaged. In the future, this class will be expanded with improvements over the standard pdb. The original code in this file is mainly lifted out of cmd.py in Python 2.2, with minor changes. Licensing should therefore be under the standard Python terms. For details on the PSF (Python Software Foundation) standard license, see: https://docs.python.org/2/license.html All the changes since then are under the same license as IPython. """ #***************************************************************************** # # This file is licensed under the PSF license. # # Copyright (C) 2001 Python Software Foundation, www.python.org # Copyright (C) 2005-2006 Fernando Perez. # # #***************************************************************************** import inspect import linecache import sys import re import os from IPython import get_ipython from IPython.utils import PyColorize from IPython.utils import coloransi, py3compat from IPython.core.excolors import exception_colors # skip module docstests __skip_doctest__ = True prompt = 'ipdb> ' # We have to check this directly from sys.argv, config struct not yet available from pdb import Pdb as OldPdb # Allow the set_trace code to operate outside of an ipython instance, even if # it does so with some limitations. The rest of this support is implemented in # the Tracer constructor. DEBUGGERSKIP = "__debuggerskip__" def make_arrow(pad): """generate the leading arrow in front of traceback or debugger""" if pad >= 2: return '-'*(pad-2) + '> ' elif pad == 1: return '>' return '' def BdbQuit_excepthook(et, ev, tb, excepthook=None): """Exception hook which handles `BdbQuit` exceptions. All other exceptions are processed using the `excepthook` parameter. """ raise ValueError( "`BdbQuit_excepthook` is deprecated since version 5.1", ) def BdbQuit_IPython_excepthook(self, et, ev, tb, tb_offset=None): raise ValueError( "`BdbQuit_IPython_excepthook` is deprecated since version 5.1", DeprecationWarning, stacklevel=2) RGX_EXTRA_INDENT = re.compile(r'(?<=\n)\s+') def strip_indentation(multiline_string): return RGX_EXTRA_INDENT.sub('', multiline_string) def decorate_fn_with_doc(new_fn, old_fn, additional_text=""): """Make new_fn have old_fn's doc string. This is particularly useful for the ``do_...`` commands that hook into the help system. Adapted from from a comp.lang.python posting by Duncan Booth.""" def wrapper(*args, **kw): return new_fn(*args, **kw) if old_fn.__doc__: wrapper.__doc__ = strip_indentation(old_fn.__doc__) + additional_text return wrapper class Pdb(OldPdb): """Modified Pdb class, does not load readline. for a standalone version that uses prompt_toolkit, see `IPython.terminal.debugger.TerminalPdb` and `IPython.terminal.debugger.set_trace()` This debugger can hide and skip frames that are tagged according to some predicates. See the `skip_predicates` commands. """ default_predicates = { "tbhide": True, "readonly": False, "ipython_internal": True, "debuggerskip": True, } def __init__(self, completekey=None, stdin=None, stdout=None, context=5, **kwargs): """Create a new IPython debugger. Parameters ---------- completekey : default None Passed to pdb.Pdb. stdin : default None Passed to pdb.Pdb. stdout : default None Passed to pdb.Pdb. context : int Number of lines of source code context to show when displaying stacktrace information. **kwargs Passed to pdb.Pdb. Notes ----- The possibilities are python version dependent, see the python docs for more info. """ # Parent constructor: try: self.context = int(context) if self.context <= 0: raise ValueError("Context must be a positive integer") except (TypeError, ValueError) as e: raise ValueError("Context must be a positive integer") from e # `kwargs` ensures full compatibility with stdlib's `pdb.Pdb`. OldPdb.__init__(self, completekey, stdin, stdout, **kwargs) # IPython changes... self.shell = get_ipython() if self.shell is None: save_main = sys.modules['__main__'] # No IPython instance running, we must create one from IPython.terminal.interactiveshell import \ TerminalInteractiveShell self.shell = TerminalInteractiveShell.instance() # needed by any code which calls __import__("__main__") after # the debugger was entered. See also #9941. sys.modules["__main__"] = save_main color_scheme = self.shell.colors self.aliases = {} # Create color table: we copy the default one from the traceback # module and add a few attributes needed for debugging self.color_scheme_table = exception_colors() # shorthands C = coloransi.TermColors cst = self.color_scheme_table cst['NoColor'].colors.prompt = C.NoColor cst['NoColor'].colors.breakpoint_enabled = C.NoColor cst['NoColor'].colors.breakpoint_disabled = C.NoColor cst['Linux'].colors.prompt = C.Green cst['Linux'].colors.breakpoint_enabled = C.LightRed cst['Linux'].colors.breakpoint_disabled = C.Red cst['LightBG'].colors.prompt = C.Blue cst['LightBG'].colors.breakpoint_enabled = C.LightRed cst['LightBG'].colors.breakpoint_disabled = C.Red cst['Neutral'].colors.prompt = C.Blue cst['Neutral'].colors.breakpoint_enabled = C.LightRed cst['Neutral'].colors.breakpoint_disabled = C.Red # Add a python parser so we can syntax highlight source while # debugging. self.parser = PyColorize.Parser(style=color_scheme) self.set_colors(color_scheme) # Set the prompt - the default prompt is '(Pdb)' self.prompt = prompt self.skip_hidden = True self.report_skipped = True # list of predicates we use to skip frames self._predicates = self.default_predicates # def set_colors(self, scheme): """Shorthand access to the color table scheme selector method.""" self.color_scheme_table.set_active_scheme(scheme) self.parser.style = scheme def set_trace(self, frame=None): if frame is None: frame = sys._getframe().f_back self.initial_frame = frame return super().set_trace(frame) def _hidden_predicate(self, frame): """ Given a frame return whether it it should be hidden or not by IPython. """ if self._predicates["readonly"]: fname = frame.f_code.co_filename # we need to check for file existence and interactively define # function would otherwise appear as RO. if os.path.isfile(fname) and not os.access(fname, os.W_OK): return True if self._predicates["tbhide"]: if frame in (self.curframe, getattr(self, "initial_frame", None)): return False frame_locals = self._get_frame_locals(frame) if "__tracebackhide__" not in frame_locals: return False return frame_locals["__tracebackhide__"] return False def hidden_frames(self, stack): """ Given an index in the stack return whether it should be skipped. This is used in up/down and where to skip frames. """ # The f_locals dictionary is updated from the actual frame # locals whenever the .f_locals accessor is called, so we # avoid calling it here to preserve self.curframe_locals. # Furthermore, there is no good reason to hide the current frame. ip_hide = [self._hidden_predicate(s[0]) for s in stack] ip_start = [i for i, s in enumerate(ip_hide) if s == "__ipython_bottom__"] if ip_start and self._predicates["ipython_internal"]: ip_hide = [h if i > ip_start[0] else True for (i, h) in enumerate(ip_hide)] return ip_hide def interaction(self, frame, traceback): try: OldPdb.interaction(self, frame, traceback) except KeyboardInterrupt: self.stdout.write("\n" + self.shell.get_exception_only()) def precmd(self, line): """Perform useful escapes on the command before it is executed.""" if line.endswith("??"): line = "pinfo2 " + line[:-2] elif line.endswith("?"): line = "pinfo " + line[:-1] line = super().precmd(line) return line def new_do_frame(self, arg): OldPdb.do_frame(self, arg) def new_do_quit(self, arg): if hasattr(self, 'old_all_completions'): self.shell.Completer.all_completions = self.old_all_completions return OldPdb.do_quit(self, arg) do_q = do_quit = decorate_fn_with_doc(new_do_quit, OldPdb.do_quit) def new_do_restart(self, arg): """Restart command. In the context of ipython this is exactly the same thing as 'quit'.""" self.msg("Restart doesn't make sense here. Using 'quit' instead.") return self.do_quit(arg) def print_stack_trace(self, context=None): Colors = self.color_scheme_table.active_colors ColorsNormal = Colors.Normal if context is None: context = self.context try: context = int(context) if context <= 0: raise ValueError("Context must be a positive integer") except (TypeError, ValueError) as e: raise ValueError("Context must be a positive integer") from e try: skipped = 0 for hidden, frame_lineno in zip(self.hidden_frames(self.stack), self.stack): if hidden and self.skip_hidden: skipped += 1 continue if skipped: print( f"{Colors.excName} [... skipping {skipped} hidden frame(s)]{ColorsNormal}\n" ) skipped = 0 self.print_stack_entry(frame_lineno, context=context) if skipped: print( f"{Colors.excName} [... skipping {skipped} hidden frame(s)]{ColorsNormal}\n" ) except KeyboardInterrupt: pass def print_stack_entry(self, frame_lineno, prompt_prefix='\n-> ', context=None): if context is None: context = self.context try: context = int(context) if context <= 0: raise ValueError("Context must be a positive integer") except (TypeError, ValueError) as e: raise ValueError("Context must be a positive integer") from e print(self.format_stack_entry(frame_lineno, '', context), file=self.stdout) # vds: >> frame, lineno = frame_lineno filename = frame.f_code.co_filename self.shell.hooks.synchronize_with_editor(filename, lineno, 0) # vds: << def _get_frame_locals(self, frame): """ " Accessing f_local of current frame reset the namespace, so we want to avoid that or the following can happen ipdb> foo "old" ipdb> foo = "new" ipdb> foo "new" ipdb> where ipdb> foo "old" So if frame is self.current_frame we instead return self.curframe_locals """ if frame is self.curframe: return self.curframe_locals else: return frame.f_locals def format_stack_entry(self, frame_lineno, lprefix=': ', context=None): if context is None: context = self.context try: context = int(context) if context <= 0: print("Context must be a positive integer", file=self.stdout) except (TypeError, ValueError): print("Context must be a positive integer", file=self.stdout) import reprlib ret = [] Colors = self.color_scheme_table.active_colors ColorsNormal = Colors.Normal tpl_link = "%s%%s%s" % (Colors.filenameEm, ColorsNormal) tpl_call = "%s%%s%s%%s%s" % (Colors.vName, Colors.valEm, ColorsNormal) tpl_line = "%%s%s%%s %s%%s" % (Colors.lineno, ColorsNormal) tpl_line_em = "%%s%s%%s %s%%s%s" % (Colors.linenoEm, Colors.line, ColorsNormal) frame, lineno = frame_lineno return_value = '' loc_frame = self._get_frame_locals(frame) if "__return__" in loc_frame: rv = loc_frame["__return__"] # return_value += '->' return_value += reprlib.repr(rv) + "\n" ret.append(return_value) #s = filename + '(' + `lineno` + ')' filename = self.canonic(frame.f_code.co_filename) link = tpl_link % py3compat.cast_unicode(filename) if frame.f_code.co_name: func = frame.f_code.co_name else: func = "" call = "" if func != "?": if "__args__" in loc_frame: args = reprlib.repr(loc_frame["__args__"]) else: args = '()' call = tpl_call % (func, args) # The level info should be generated in the same format pdb uses, to # avoid breaking the pdbtrack functionality of python-mode in *emacs. if frame is self.curframe: ret.append('> ') else: ret.append(" ") ret.append("%s(%s)%s\n" % (link, lineno, call)) start = lineno - 1 - context//2 lines = linecache.getlines(filename) start = min(start, len(lines) - context) start = max(start, 0) lines = lines[start : start + context] for i, line in enumerate(lines): show_arrow = start + 1 + i == lineno linetpl = (frame is self.curframe or show_arrow) and tpl_line_em or tpl_line ret.append( self.__format_line( linetpl, filename, start + 1 + i, line, arrow=show_arrow ) ) return "".join(ret) def __format_line(self, tpl_line, filename, lineno, line, arrow=False): bp_mark = "" bp_mark_color = "" new_line, err = self.parser.format2(line, 'str') if not err: line = new_line bp = None if lineno in self.get_file_breaks(filename): bps = self.get_breaks(filename, lineno) bp = bps[-1] if bp: Colors = self.color_scheme_table.active_colors bp_mark = str(bp.number) bp_mark_color = Colors.breakpoint_enabled if not bp.enabled: bp_mark_color = Colors.breakpoint_disabled numbers_width = 7 if arrow: # This is the line with the error pad = numbers_width - len(str(lineno)) - len(bp_mark) num = '%s%s' % (make_arrow(pad), str(lineno)) else: num = '%*s' % (numbers_width - len(bp_mark), str(lineno)) return tpl_line % (bp_mark_color + bp_mark, num, line) def print_list_lines(self, filename, first, last): """The printing (as opposed to the parsing part of a 'list' command.""" try: Colors = self.color_scheme_table.active_colors ColorsNormal = Colors.Normal tpl_line = '%%s%s%%s %s%%s' % (Colors.lineno, ColorsNormal) tpl_line_em = '%%s%s%%s %s%%s%s' % (Colors.linenoEm, Colors.line, ColorsNormal) src = [] if filename == "" and hasattr(self, "_exec_filename"): filename = self._exec_filename for lineno in range(first, last+1): line = linecache.getline(filename, lineno) if not line: break if lineno == self.curframe.f_lineno: line = self.__format_line( tpl_line_em, filename, lineno, line, arrow=True ) else: line = self.__format_line( tpl_line, filename, lineno, line, arrow=False ) src.append(line) self.lineno = lineno print(''.join(src), file=self.stdout) except KeyboardInterrupt: pass def do_skip_predicates(self, args): """ Turn on/off individual predicates as to whether a frame should be hidden/skip. The global option to skip (or not) hidden frames is set with skip_hidden To change the value of a predicate skip_predicates key [true|false] Call without arguments to see the current values. To permanently change the value of an option add the corresponding command to your ``~/.pdbrc`` file. If you are programmatically using the Pdb instance you can also change the ``default_predicates`` class attribute. """ if not args.strip(): print("current predicates:") for p, v in self._predicates.items(): print(" ", p, ":", v) return type_value = args.strip().split(" ") if len(type_value) != 2: print( f"Usage: skip_predicates , with one of {set(self._predicates.keys())}" ) return type_, value = type_value if type_ not in self._predicates: print(f"{type_!r} not in {set(self._predicates.keys())}") return if value.lower() not in ("true", "yes", "1", "no", "false", "0"): print( f"{value!r} is invalid - use one of ('true', 'yes', '1', 'no', 'false', '0')" ) return self._predicates[type_] = value.lower() in ("true", "yes", "1") if not any(self._predicates.values()): print( "Warning, all predicates set to False, skip_hidden may not have any effects." ) def do_skip_hidden(self, arg): """ Change whether or not we should skip frames with the __tracebackhide__ attribute. """ if not arg.strip(): print( f"skip_hidden = {self.skip_hidden}, use 'yes','no', 'true', or 'false' to change." ) elif arg.strip().lower() in ("true", "yes"): self.skip_hidden = True elif arg.strip().lower() in ("false", "no"): self.skip_hidden = False if not any(self._predicates.values()): print( "Warning, all predicates set to False, skip_hidden may not have any effects." ) def do_list(self, arg): """Print lines of code from the current stack frame """ self.lastcmd = 'list' last = None if arg and arg != ".": try: x = eval(arg, {}, {}) if type(x) == type(()): first, last = x first = int(first) last = int(last) if last < first: # Assume it's a count last = first + last else: first = max(1, int(x) - 5) except: print('*** Error in argument:', repr(arg), file=self.stdout) return elif self.lineno is None or arg == ".": first = max(1, self.curframe.f_lineno - 5) else: first = self.lineno + 1 if last is None: last = first + 10 self.print_list_lines(self.curframe.f_code.co_filename, first, last) # vds: >> lineno = first filename = self.curframe.f_code.co_filename self.shell.hooks.synchronize_with_editor(filename, lineno, 0) # vds: << do_l = do_list def getsourcelines(self, obj): lines, lineno = inspect.findsource(obj) if inspect.isframe(obj) and obj.f_globals is self._get_frame_locals(obj): # must be a module frame: do not try to cut a block out of it return lines, 1 elif inspect.ismodule(obj): return lines, 1 return inspect.getblock(lines[lineno:]), lineno+1 def do_longlist(self, arg): """Print lines of code from the current stack frame. Shows more lines than 'list' does. """ self.lastcmd = 'longlist' try: lines, lineno = self.getsourcelines(self.curframe) except OSError as err: self.error(err) return last = lineno + len(lines) self.print_list_lines(self.curframe.f_code.co_filename, lineno, last) do_ll = do_longlist def do_debug(self, arg): """debug code Enter a recursive debugger that steps through the code argument (which is an arbitrary expression or statement to be executed in the current environment). """ trace_function = sys.gettrace() sys.settrace(None) globals = self.curframe.f_globals locals = self.curframe_locals p = self.__class__(completekey=self.completekey, stdin=self.stdin, stdout=self.stdout) p.use_rawinput = self.use_rawinput p.prompt = "(%s) " % self.prompt.strip() self.message("ENTERING RECURSIVE DEBUGGER") sys.call_tracing(p.run, (arg, globals, locals)) self.message("LEAVING RECURSIVE DEBUGGER") sys.settrace(trace_function) self.lastcmd = p.lastcmd def do_pdef(self, arg): """Print the call signature for any callable object. The debugger interface to %pdef""" namespaces = [ ("Locals", self.curframe_locals), ("Globals", self.curframe.f_globals), ] self.shell.find_line_magic("pdef")(arg, namespaces=namespaces) def do_pdoc(self, arg): """Print the docstring for an object. The debugger interface to %pdoc.""" namespaces = [ ("Locals", self.curframe_locals), ("Globals", self.curframe.f_globals), ] self.shell.find_line_magic("pdoc")(arg, namespaces=namespaces) def do_pfile(self, arg): """Print (or run through pager) the file where an object is defined. The debugger interface to %pfile. """ namespaces = [ ("Locals", self.curframe_locals), ("Globals", self.curframe.f_globals), ] self.shell.find_line_magic("pfile")(arg, namespaces=namespaces) def do_pinfo(self, arg): """Provide detailed information about an object. The debugger interface to %pinfo, i.e., obj?.""" namespaces = [ ("Locals", self.curframe_locals), ("Globals", self.curframe.f_globals), ] self.shell.find_line_magic("pinfo")(arg, namespaces=namespaces) def do_pinfo2(self, arg): """Provide extra detailed information about an object. The debugger interface to %pinfo2, i.e., obj??.""" namespaces = [ ("Locals", self.curframe_locals), ("Globals", self.curframe.f_globals), ] self.shell.find_line_magic("pinfo2")(arg, namespaces=namespaces) def do_psource(self, arg): """Print (or run through pager) the source code for an object.""" namespaces = [ ("Locals", self.curframe_locals), ("Globals", self.curframe.f_globals), ] self.shell.find_line_magic("psource")(arg, namespaces=namespaces) def do_where(self, arg): """w(here) Print a stack trace, with the most recent frame at the bottom. An arrow indicates the "current frame", which determines the context of most commands. 'bt' is an alias for this command. Take a number as argument as an (optional) number of context line to print""" if arg: try: context = int(arg) except ValueError as err: self.error(err) return self.print_stack_trace(context) else: self.print_stack_trace() do_w = do_where def break_anywhere(self, frame): """ _stop_in_decorator_internals is overly restrictive, as we may still want to trace function calls, so we need to also update break_anywhere so that is we don't `stop_here`, because of debugger skip, we may still stop at any point inside the function """ sup = super().break_anywhere(frame) if sup: return sup if self._predicates["debuggerskip"]: if DEBUGGERSKIP in frame.f_code.co_varnames: return True if frame.f_back and self._get_frame_locals(frame.f_back).get(DEBUGGERSKIP): return True return False def _is_in_decorator_internal_and_should_skip(self, frame): """ Utility to tell us whether we are in a decorator internal and should stop. """ # if we are disabled don't skip if not self._predicates["debuggerskip"]: return False # if frame is tagged, skip by default. if DEBUGGERSKIP in frame.f_code.co_varnames: return True # if one of the parent frame value set to True skip as well. cframe = frame while getattr(cframe, "f_back", None): cframe = cframe.f_back if self._get_frame_locals(cframe).get(DEBUGGERSKIP): return True return False def stop_here(self, frame): if self._is_in_decorator_internal_and_should_skip(frame) is True: return False hidden = False if self.skip_hidden: hidden = self._hidden_predicate(frame) if hidden: if self.report_skipped: Colors = self.color_scheme_table.active_colors ColorsNormal = Colors.Normal print( f"{Colors.excName} [... skipped 1 hidden frame]{ColorsNormal}\n" ) return super().stop_here(frame) def do_up(self, arg): """u(p) [count] Move the current frame count (default one) levels up in the stack trace (to an older frame). Will skip hidden frames. """ # modified version of upstream that skips # frames with __tracebackhide__ if self.curindex == 0: self.error("Oldest frame") return try: count = int(arg or 1) except ValueError: self.error("Invalid frame count (%s)" % arg) return skipped = 0 if count < 0: _newframe = 0 else: counter = 0 hidden_frames = self.hidden_frames(self.stack) for i in range(self.curindex - 1, -1, -1): if hidden_frames[i] and self.skip_hidden: skipped += 1 continue counter += 1 if counter >= count: break else: # if no break occurred. self.error( "all frames above hidden, use `skip_hidden False` to get get into those." ) return Colors = self.color_scheme_table.active_colors ColorsNormal = Colors.Normal _newframe = i self._select_frame(_newframe) if skipped: print( f"{Colors.excName} [... skipped {skipped} hidden frame(s)]{ColorsNormal}\n" ) def do_down(self, arg): """d(own) [count] Move the current frame count (default one) levels down in the stack trace (to a newer frame). Will skip hidden frames. """ if self.curindex + 1 == len(self.stack): self.error("Newest frame") return try: count = int(arg or 1) except ValueError: self.error("Invalid frame count (%s)" % arg) return if count < 0: _newframe = len(self.stack) - 1 else: counter = 0 skipped = 0 hidden_frames = self.hidden_frames(self.stack) for i in range(self.curindex + 1, len(self.stack)): if hidden_frames[i] and self.skip_hidden: skipped += 1 continue counter += 1 if counter >= count: break else: self.error( "all frames below hidden, use `skip_hidden False` to get get into those." ) return Colors = self.color_scheme_table.active_colors ColorsNormal = Colors.Normal if skipped: print( f"{Colors.excName} [... skipped {skipped} hidden frame(s)]{ColorsNormal}\n" ) _newframe = i self._select_frame(_newframe) do_d = do_down do_u = do_up def do_context(self, context): """context number_of_lines Set the number of lines of source code to show when displaying stacktrace information. """ try: new_context = int(context) if new_context <= 0: raise ValueError() self.context = new_context except ValueError: self.error("The 'context' command requires a positive integer argument.") class InterruptiblePdb(Pdb): """Version of debugger where KeyboardInterrupt exits the debugger altogether.""" def cmdloop(self, intro=None): """Wrap cmdloop() such that KeyboardInterrupt stops the debugger.""" try: return OldPdb.cmdloop(self, intro=intro) except KeyboardInterrupt: self.stop_here = lambda frame: False self.do_quit("") sys.settrace(None) self.quitting = False raise def _cmdloop(self): while True: try: # keyboard interrupts allow for an easy way to cancel # the current command, so allow them during interactive input self.allow_kbdint = True self.cmdloop() self.allow_kbdint = False break except KeyboardInterrupt: self.message('--KeyboardInterrupt--') raise def set_trace(frame=None): """ Start debugging from `frame`. If frame is not specified, debugging starts from caller's frame. """ Pdb().set_trace(frame or sys._getframe().f_back)