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+:mod:`bdb` --- Debugger framework
+=================================
+
+.. module:: bdb
+ :synopsis: Debugger framework.
+
+The :mod:`bdb` module handles basic debugger functions, like setting breakpoints
+or managing execution via the debugger.
+
+The following exception is defined:
+
+.. exception:: BdbQuit
+
+ Exception raised by the :class:`Bdb` class for quitting the debugger.
+
+
+The :mod:`bdb` module also defines two classes:
+
+.. class:: Breakpoint(self, file, line[, temporary=0[, cond=None [, funcname=None]]])
+
+ This class implements temporary breakpoints, ignore counts, disabling and
+ (re-)enabling, and conditionals.
+
+ Breakpoints are indexed by number through a list called :attr:`bpbynumber`
+ and by ``(file, line)`` pairs through :attr:`bplist`. The former points to a
+ single instance of class :class:`Breakpoint`. The latter points to a list of
+ such instances since there may be more than one breakpoint per line.
+
+ When creating a breakpoint, its associated filename should be in canonical
+ form. If a *funcname* is defined, a breakpoint hit will be counted when the
+ first line of that function is executed. A conditional breakpoint always
+ counts a hit.
+
+ :class:`Breakpoint` instances have the following methods:
+
+ .. method:: deleteMe()
+
+ Delete the breakpoint from the list associated to a file/line. If it is
+ the last breakpoint in that position, it also deletes the entry for the
+ file/line.
+
+
+ .. method:: enable()
+
+ Mark the breakpoint as enabled.
+
+
+ .. method:: disable()
+
+ Mark the breakpoint as disabled.
+
+
+ .. method:: pprint([out])
+
+ Print all the information about the breakpoint:
+
+ * The breakpoint number.
+ * If it is temporary or not.
+ * Its file,line position.
+ * The condition that causes a break.
+ * If it must be ignored the next N times.
+ * The breakpoint hit count.
+
+
+.. class:: Bdb()
+
+ The :class:`Bdb` acts as a generic Python debugger base class.
+
+ This class takes care of the details of the trace facility; a derived class
+ should implement user interaction. The standard debugger class
+ (:class:`pdb.Pdb`) is an example.
+
+
+ The following methods of :class:`Bdb` normally don't need to be overridden.
+
+ .. method:: canonic(filename)
+
+ Auxiliary method for getting a filename in a canonical form, that is, as a
+ case-normalized (on case-insensitive filesystems) absolute path, stripped
+ of surrounding angle brackets.
+
+ .. method:: reset()
+
+ Set the :attr:`botframe`, :attr:`stopframe`, :attr:`returnframe` and
+ :attr:`quitting` attributes with values ready to start debugging.
+
+ .. method:: trace_dispatch(frame, event, arg)
+
+ This function is installed as the trace function of debugged frames. Its
+ return value is the new trace function (in most cases, that is, itself).
+
+ The default implementation decides how to dispatch a frame, depending on
+ the type of event (passed as a string) that is about to be executed.
+ *event* can be one of the following:
+
+ * ``"line"``: A new line of code is going to be executed.
+ * ``"call"``: A function is about to be called, or another code block
+ entered.
+ * ``"return"``: A function or other code block is about to return.
+ * ``"exception"``: An exception has occurred.
+ * ``"c_call"``: A C function is about to be called.
+ * ``"c_return"``: A C function has returned.
+ * ``"c_exception"``: A C function has thrown an exception.
+
+ For the Python events, specialized functions (see below) are called. For
+ the C events, no action is taken.
+
+ The *arg* parameter depends on the previous event.
+
+ For more information on trace functions, see :ref:`debugger-hooks`. For
+ more information on code and frame objects, refer to :ref:`types`.
+
+ .. method:: dispatch_line(frame)
+
+ If the debugger should stop on the current line, invoke the
+ :meth:`user_line` method (which should be overridden in subclasses).
+ Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
+ (which can be set from :meth:`user_line`). Return a reference to the
+ :meth:`trace_dispatch` method for further tracing in that scope.
+
+ .. method:: dispatch_call(frame, arg)
+
+ If the debugger should stop on this function call, invoke the
+ :meth:`user_call` method (which should be overridden in subclasses).
+ Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
+ (which can be set from :meth:`user_call`). Return a reference to the
+ :meth:`trace_dispatch` method for further tracing in that scope.
+
+ .. method:: dispatch_return(frame, arg)
+
+ If the debugger should stop on this function return, invoke the
+ :meth:`user_return` method (which should be overridden in subclasses).
+ Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
+ (which can be set from :meth:`user_return`). Return a reference to the
+ :meth:`trace_dispatch` method for further tracing in that scope.
+
+ .. method:: dispatch_exception(frame, arg)
+
+ If the debugger should stop at this exception, invokes the
+ :meth:`user_exception` method (which should be overridden in subclasses).
+ Raise a :exc:`BdbQuit` exception if the :attr:`Bdb.quitting` flag is set
+ (which can be set from :meth:`user_exception`). Return a reference to the
+ :meth:`trace_dispatch` method for further tracing in that scope.
+
+ Normally derived classes don't override the following methods, but they may
+ if they want to redefine the definition of stopping and breakpoints.
+
+ .. method:: stop_here(frame)
+
+ This method checks if the *frame* is somewhere below :attr:`botframe` in
+ the call stack. :attr:`botframe` is the frame in which debugging started.
+
+ .. method:: break_here(frame)
+
+ This method checks if there is a breakpoint in the filename and line
+ belonging to *frame* or, at least, in the current function. If the
+ breakpoint is a temporary one, this method deletes it.
+
+ .. method:: break_anywhere(frame)
+
+ This method checks if there is a breakpoint in the filename of the current
+ frame.
+
+ Derived classes should override these methods to gain control over debugger
+ operation.
+
+ .. method:: user_call(frame, argument_list)
+
+ This method is called from :meth:`dispatch_call` when there is the
+ possibility that a break might be necessary anywhere inside the called
+ function.
+
+ .. method:: user_line(frame)
+
+ This method is called from :meth:`dispatch_line` when either
+ :meth:`stop_here` or :meth:`break_here` yields True.
+
+ .. method:: user_return(frame, return_value)
+
+ This method is called from :meth:`dispatch_return` when :meth:`stop_here`
+ yields True.
+
+ .. method:: user_exception(frame, exc_info)
+
+ This method is called from :meth:`dispatch_exception` when
+ :meth:`stop_here` yields True.
+
+ .. method:: do_clear(arg)
+
+ Handle how a breakpoint must be removed when it is a temporary one.
+
+ This method must be implemented by derived classes.
+
+
+ Derived classes and clients can call the following methods to affect the
+ stepping state.
+
+ .. method:: set_step()
+
+ Stop after one line of code.
+
+ .. method:: set_next(frame)
+
+ Stop on the next line in or below the given frame.
+
+ .. method:: set_return(frame)
+
+ Stop when returning from the given frame.
+
+ .. method:: set_until(frame)
+
+ Stop when the line with the line no greater than the current one is
+ reached or when returning from current frame
+
+ .. method:: set_trace([frame])
+
+ Start debugging from *frame*. If *frame* is not specified, debugging
+ starts from caller's frame.
+
+ .. method:: set_continue()
+
+ Stop only at breakpoints or when finished. If there are no breakpoints,
+ set the system trace function to None.
+
+ .. method:: set_quit()
+
+ Set the :attr:`quitting` attribute to True. This raises :exc:`BdbQuit` in
+ the next call to one of the :meth:`dispatch_\*` methods.
+
+
+ Derived classes and clients can call the following methods to manipulate
+ breakpoints. These methods return a string containing an error message if
+ something went wrong, or ``None`` if all is well.
+
+ .. method:: set_break(filename, lineno[, temporary=0[, cond[, funcname]]])
+
+ Set a new breakpoint. If the *lineno* line doesn't exist for the
+ *filename* passed as argument, return an error message. The *filename*
+ should be in canonical form, as described in the :meth:`canonic` method.
+
+ .. method:: clear_break(filename, lineno)
+
+ Delete the breakpoints in *filename* and *lineno*. If none were set, an
+ error message is returned.
+
+ .. method:: clear_bpbynumber(arg)
+
+ Delete the breakpoint which has the index *arg* in the
+ :attr:`Breakpoint.bpbynumber`. If *arg* is not numeric or out of range,
+ return an error message.
+
+ .. method:: clear_all_file_breaks(filename)
+
+ Delete all breakpoints in *filename*. If none were set, an error message
+ is returned.
+
+ .. method:: clear_all_breaks()
+
+ Delete all existing breakpoints.
+
+ .. method:: get_break(filename, lineno)
+
+ Check if there is a breakpoint for *lineno* of *filename*.
+
+ .. method:: get_breaks(filename, lineno)
+
+ Return all breakpoints for *lineno* in *filename*, or an empty list if
+ none are set.
+
+ .. method:: get_file_breaks(filename)
+
+ Return all breakpoints in *filename*, or an empty list if none are set.
+
+ .. method:: get_all_breaks()
+
+ Return all breakpoints that are set.
+
+
+ Derived classes and clients can call the following methods to get a data
+ structure representing a stack trace.
+
+ .. method:: get_stack(f, t)
+
+ Get a list of records for a frame and all higher (calling) and lower
+ frames, and the size of the higher part.
+
+ .. method:: format_stack_entry(frame_lineno, [lprefix=': '])
+
+ Return a string with information about a stack entry, identified by a
+ ``(frame, lineno)`` tuple:
+
+ * The canonical form of the filename which contains the frame.
+ * The function name, or ``"<lambda>"``.
+ * The input arguments.
+ * The return value.
+ * The line of code (if it exists).
+
+
+ The following two methods can be called by clients to use a debugger to debug
+ a :term:`statement`, given as a string.
+
+ .. method:: run(cmd, [globals, [locals]])
+
+ Debug a statement executed via the :keyword:`exec` statement. *globals*
+ defaults to :attr:`__main__.__dict__`, *locals* defaults to *globals*.
+
+ .. method:: runeval(expr, [globals, [locals]])
+
+ Debug an expression executed via the :func:`eval` function. *globals* and
+ *locals* have the same meaning as in :meth:`run`.
+
+ .. method:: runctx(cmd, globals, locals)
+
+ For backwards compatibility. Calls the :meth:`run` method.
+
+ .. method:: runcall(func, *args, **kwds)
+
+ Debug a single function call, and return its result.
+
+
+Finally, the module defines the following functions:
+
+.. function:: checkfuncname(b, frame)
+
+ Check whether we should break here, depending on the way the breakpoint *b*
+ was set.
+
+ If it was set via line number, it checks if ``b.line`` is the same as the one
+ in the frame also passed as argument. If the breakpoint was set via function
+ name, we have to check we are in the right frame (the right function) and if
+ we are in its first executable line.
+
+.. function:: effective(file, line, frame)
+
+ Determine if there is an effective (active) breakpoint at this line of code.
+ Return breakpoint number or 0 if none.
+
+ Called only if we know there is a breakpoint at this location. Returns the
+ breakpoint that was triggered and a flag that indicates if it is ok to delete
+ a temporary breakpoint.
+
+.. function:: set_trace()
+
+ Starts debugging with a :class:`Bdb` instance from caller's frame.