1 :mod:`bdb` --- Debugger framework
2 =================================
5 :synopsis: Debugger framework.
7 The :mod:`bdb` module handles basic debugger functions, like setting breakpoints
8 or managing execution via the debugger.
10 The following exception is defined:
12 .. exception:: BdbQuit
14 Exception raised by the :class:`Bdb` class for quitting the debugger.
17 The :mod:`bdb` module also defines two classes:
19 .. class:: Breakpoint(self, file, line[, temporary=0[, cond=None [, funcname=None]]])
21 This class implements temporary breakpoints, ignore counts, disabling and
22 (re-)enabling, and conditionals.
24 Breakpoints are indexed by number through a list called :attr:`bpbynumber`
25 and by ``(file, line)`` pairs through :attr:`bplist`. The former points to a
26 single instance of class :class:`Breakpoint`. The latter points to a list of
27 such instances since there may be more than one breakpoint per line.
29 When creating a breakpoint, its associated filename should be in canonical
30 form. If a *funcname* is defined, a breakpoint hit will be counted when the
31 first line of that function is executed. A conditional breakpoint always
34 :class:`Breakpoint` instances have the following methods:
36 .. method:: deleteMe()
38 Delete the breakpoint from the list associated to a file/line. If it is
39 the last breakpoint in that position, it also deletes the entry for the
45 Mark the breakpoint as enabled.
50 Mark the breakpoint as disabled.
53 .. method:: pprint([out])
55 Print all the information about the breakpoint:
57 * The breakpoint number.
58 * If it is temporary or not.
59 * Its file,line position.
60 * The condition that causes a break.
61 * If it must be ignored the next N times.
62 * The breakpoint hit count.
65 .. class:: Bdb(skip=None)
67 The :class:`Bdb` class acts as a generic Python debugger base class.
69 This class takes care of the details of the trace facility; a derived class
70 should implement user interaction. The standard debugger class
71 (:class:`pdb.Pdb`) is an example.
73 The *skip* argument, if given, must be an iterable of glob-style
74 module name patterns. The debugger will not step into frames that
75 originate in a module that matches one of these patterns. Whether a
76 frame is considered to originate in a certain module is determined
77 by the ``__name__`` in the frame globals.
82 The following methods of :class:`Bdb` normally don't need to be overridden.
84 .. method:: canonic(filename)
86 Auxiliary method for getting a filename in a canonical form, that is, as a
87 case-normalized (on case-insensitive filesystems) absolute path, stripped
88 of surrounding angle brackets.
92 Set the :attr:`botframe`, :attr:`stopframe`, :attr:`returnframe` and
93 :attr:`quitting` attributes with values ready to start debugging.
95 .. method:: trace_dispatch(frame, event, arg)
97 This function is installed as the trace function of debugged frames. Its
98 return value is the new trace function (in most cases, that is, itself).
100 The default implementation decides how to dispatch a frame, depending on
101 the type of event (passed as a string) that is about to be executed.
102 *event* can be one of the following:
104 * ``"line"``: A new line of code is going to be executed.
105 * ``"call"``: A function is about to be called, or another code block
107 * ``"return"``: A function or other code block is about to return.
108 * ``"exception"``: An exception has occurred.
109 * ``"c_call"``: A C function is about to be called.
110 * ``"c_return"``: A C function has returned.
111 * ``"c_exception"``: A C function has thrown an exception.
113 For the Python events, specialized functions (see below) are called. For
114 the C events, no action is taken.
116 The *arg* parameter depends on the previous event.
118 See the documentation for :func:`sys.settrace` for more information on the
119 trace function. For more information on code and frame objects, refer to
122 .. method:: dispatch_line(frame)
124 If the debugger should stop on the current line, invoke the
125 :meth:`user_line` method (which should be overridden in subclasses).
126 Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
127 (which can be set from :meth:`user_line`). Return a reference to the
128 :meth:`trace_dispatch` method for further tracing in that scope.
130 .. method:: dispatch_call(frame, arg)
132 If the debugger should stop on this function call, invoke the
133 :meth:`user_call` method (which should be overridden in subclasses).
134 Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
135 (which can be set from :meth:`user_call`). Return a reference to the
136 :meth:`trace_dispatch` method for further tracing in that scope.
138 .. method:: dispatch_return(frame, arg)
140 If the debugger should stop on this function return, invoke the
141 :meth:`user_return` method (which should be overridden in subclasses).
142 Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
143 (which can be set from :meth:`user_return`). Return a reference to the
144 :meth:`trace_dispatch` method for further tracing in that scope.
146 .. method:: dispatch_exception(frame, arg)
148 If the debugger should stop at this exception, invokes the
149 :meth:`user_exception` method (which should be overridden in subclasses).
150 Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
151 (which can be set from :meth:`user_exception`). Return a reference to the
152 :meth:`trace_dispatch` method for further tracing in that scope.
154 Normally derived classes don't override the following methods, but they may
155 if they want to redefine the definition of stopping and breakpoints.
157 .. method:: stop_here(frame)
159 This method checks if the *frame* is somewhere below :attr:`botframe` in
160 the call stack. :attr:`botframe` is the frame in which debugging started.
162 .. method:: break_here(frame)
164 This method checks if there is a breakpoint in the filename and line
165 belonging to *frame* or, at least, in the current function. If the
166 breakpoint is a temporary one, this method deletes it.
168 .. method:: break_anywhere(frame)
170 This method checks if there is a breakpoint in the filename of the current
173 Derived classes should override these methods to gain control over debugger
176 .. method:: user_call(frame, argument_list)
178 This method is called from :meth:`dispatch_call` when there is the
179 possibility that a break might be necessary anywhere inside the called
182 .. method:: user_line(frame)
184 This method is called from :meth:`dispatch_line` when either
185 :meth:`stop_here` or :meth:`break_here` yields True.
187 .. method:: user_return(frame, return_value)
189 This method is called from :meth:`dispatch_return` when :meth:`stop_here`
192 .. method:: user_exception(frame, exc_info)
194 This method is called from :meth:`dispatch_exception` when
195 :meth:`stop_here` yields True.
197 .. method:: do_clear(arg)
199 Handle how a breakpoint must be removed when it is a temporary one.
201 This method must be implemented by derived classes.
204 Derived classes and clients can call the following methods to affect the
207 .. method:: set_step()
209 Stop after one line of code.
211 .. method:: set_next(frame)
213 Stop on the next line in or below the given frame.
215 .. method:: set_return(frame)
217 Stop when returning from the given frame.
219 .. method:: set_until(frame)
221 Stop when the line with the line no greater than the current one is
222 reached or when returning from current frame
224 .. method:: set_trace([frame])
226 Start debugging from *frame*. If *frame* is not specified, debugging
227 starts from caller's frame.
229 .. method:: set_continue()
231 Stop only at breakpoints or when finished. If there are no breakpoints,
232 set the system trace function to None.
234 .. method:: set_quit()
236 Set the :attr:`quitting` attribute to True. This raises :exc:`BdbQuit` in
237 the next call to one of the :meth:`dispatch_\*` methods.
240 Derived classes and clients can call the following methods to manipulate
241 breakpoints. These methods return a string containing an error message if
242 something went wrong, or ``None`` if all is well.
244 .. method:: set_break(filename, lineno[, temporary=0[, cond[, funcname]]])
246 Set a new breakpoint. If the *lineno* line doesn't exist for the
247 *filename* passed as argument, return an error message. The *filename*
248 should be in canonical form, as described in the :meth:`canonic` method.
250 .. method:: clear_break(filename, lineno)
252 Delete the breakpoints in *filename* and *lineno*. If none were set, an
253 error message is returned.
255 .. method:: clear_bpbynumber(arg)
257 Delete the breakpoint which has the index *arg* in the
258 :attr:`Breakpoint.bpbynumber`. If *arg* is not numeric or out of range,
259 return an error message.
261 .. method:: clear_all_file_breaks(filename)
263 Delete all breakpoints in *filename*. If none were set, an error message
266 .. method:: clear_all_breaks()
268 Delete all existing breakpoints.
270 .. method:: get_break(filename, lineno)
272 Check if there is a breakpoint for *lineno* of *filename*.
274 .. method:: get_breaks(filename, lineno)
276 Return all breakpoints for *lineno* in *filename*, or an empty list if
279 .. method:: get_file_breaks(filename)
281 Return all breakpoints in *filename*, or an empty list if none are set.
283 .. method:: get_all_breaks()
285 Return all breakpoints that are set.
288 Derived classes and clients can call the following methods to get a data
289 structure representing a stack trace.
291 .. method:: get_stack(f, t)
293 Get a list of records for a frame and all higher (calling) and lower
294 frames, and the size of the higher part.
296 .. method:: format_stack_entry(frame_lineno, [lprefix=': '])
298 Return a string with information about a stack entry, identified by a
299 ``(frame, lineno)`` tuple:
301 * The canonical form of the filename which contains the frame.
302 * The function name, or ``"<lambda>"``.
303 * The input arguments.
305 * The line of code (if it exists).
308 The following two methods can be called by clients to use a debugger to debug
309 a :term:`statement`, given as a string.
311 .. method:: run(cmd, [globals, [locals]])
313 Debug a statement executed via the :keyword:`exec` statement. *globals*
314 defaults to :attr:`__main__.__dict__`, *locals* defaults to *globals*.
316 .. method:: runeval(expr, [globals, [locals]])
318 Debug an expression executed via the :func:`eval` function. *globals* and
319 *locals* have the same meaning as in :meth:`run`.
321 .. method:: runctx(cmd, globals, locals)
323 For backwards compatibility. Calls the :meth:`run` method.
325 .. method:: runcall(func, *args, **kwds)
327 Debug a single function call, and return its result.
330 Finally, the module defines the following functions:
332 .. function:: checkfuncname(b, frame)
334 Check whether we should break here, depending on the way the breakpoint *b*
337 If it was set via line number, it checks if ``b.line`` is the same as the one
338 in the frame also passed as argument. If the breakpoint was set via function
339 name, we have to check we are in the right frame (the right function) and if
340 we are in its first executable line.
342 .. function:: effective(file, line, frame)
344 Determine if there is an effective (active) breakpoint at this line of code.
345 Return breakpoint number or 0 if none.
347 Called only if we know there is a breakpoint at this location. Returns the
348 breakpoint that was triggered and a flag that indicates if it is ok to delete
349 a temporary breakpoint.
351 .. function:: set_trace()
353 Starts debugging with a :class:`Bdb` instance from caller's frame.