| :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() |
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| Mark the breakpoint as enabled. |
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| .. method:: disable() |
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| Mark the breakpoint as disabled. |
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| .. method:: pprint([out]) |
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| 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. |
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| .. method:: user_line(frame) |
| |
| This method is called from :meth:`dispatch_line` when either |
| :meth:`stop_here` or :meth:`break_here` yields True. |
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| .. method:: user_return(frame, return_value) |
| |
| This method is called from :meth:`dispatch_return` when :meth:`stop_here` |
| yields True. |
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| .. method:: user_exception(frame, exc_info) |
| |
| This method is called from :meth:`dispatch_exception` when |
| :meth:`stop_here` yields True. |
| |
| .. method:: do_clear(arg) |
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| 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. |
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| .. method:: set_step() |
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| Stop after one line of code. |
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| .. method:: set_next(frame) |
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| Stop on the next line in or below the given frame. |
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| .. method:: set_return(frame) |
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| Stop when returning from the given frame. |
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| .. method:: set_until(frame) |
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| Stop when the line with the line no greater than the current one is |
| reached or when returning from current frame |
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| .. method:: set_trace([frame]) |
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| Start debugging from *frame*. If *frame* is not specified, debugging |
| starts from caller's frame. |
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| .. method:: set_continue() |
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| Stop only at breakpoints or when finished. If there are no breakpoints, |
| set the system trace function to None. |
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| .. 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. |
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| .. 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. |
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| .. method:: clear_all_file_breaks(filename) |
| |
| Delete all breakpoints in *filename*. If none were set, an error message |
| is returned. |
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| .. method:: clear_all_breaks() |
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| Delete all existing breakpoints. |
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| .. method:: get_break(filename, lineno) |
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| Check if there is a breakpoint for *lineno* of *filename*. |
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| .. method:: get_breaks(filename, lineno) |
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| Return all breakpoints for *lineno* in *filename*, or an empty list if |
| none are set. |
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| .. method:: get_file_breaks(filename) |
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| Return all breakpoints in *filename*, or an empty list if none are set. |
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| .. method:: get_all_breaks() |
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| Return all breakpoints that are set. |
| |
| |
| Derived classes and clients can call the following methods to get a data |
| structure representing a stack trace. |
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| .. 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 :func:`exec` function. *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`. |
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| .. method:: runctx(cmd, globals, locals) |
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| For backwards compatibility. Calls the :meth:`run` method. |
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| .. method:: runcall(func, *args, **kwds) |
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| Debug a single function call, and return its result. |
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| Finally, the module defines the following functions: |
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| .. function:: checkfuncname(b, frame) |
| |
| Check whether we should break here, depending on the way the breakpoint *b* |
| was set. |
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| 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. |
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| .. function:: set_trace() |
| |
| Starts debugging with a :class:`Bdb` instance from caller's frame. |