The Extended Python Debugger Pydb
=======================

To use the debugger in its simplest form:

        >>> import pydb
        >>> pydb.run('<a statement>')

The debugger's prompt is '(Pydb) '.  This will stop in the first
function call in <a statement>.

Alternatively, if a statement terminated with an unhandled exception,
you can use pydb's post-mortem facility to inspect the contents of the
traceback:

        >>> <a statement>
        <exception traceback>
        >>> import pydb
        >>> pydb.pm()

The commands recognized by the debugger are listed in the next
section.  Most can be abbreviated as indicated; e.g., h(elp) means
that 'help' can be typed as 'h' or 'help' (but not as 'he' or 'hel',
nor as 'H' or 'Help' or 'HELP').  Optional arguments are enclosed in
square brackets.

A blank line repeats the previous command literally, except for
'list', where it lists the next 11 lines.

Commands that the debugger doesn't recognize are assumed to be Python
statements and are executed in the context of the program being
debugged.  Python statements can also be prefixed with an exclamation
point ('!').  This is a powerful way to inspect the program being
debugged; it is even possible to change variables.  When an exception
occurs in such a statement, the exception name is printed but the
debugger's state is not changed.

The debugger supports aliases, which can save typing.  And aliases can
have parameters (see the alias help entry) which allows one a certain
level of adaptability to the context under examination.

Multiple commands may be entered on a single line, separated by the
pair ';;'.  No intelligence is applied to separating the commands; the
input is split at the first ';;', even if it is in the middle of a
quoted string.

If a file ".pydbrc" exists in your home directory or in the current
directory, it is read in and executed as if it had been typed at the
debugger prompt.  This is particularly useful for aliases.  If both
files exist, the one in the home directory is read first and aliases
defined there can be overriden by the local file.

Aside from aliases, the debugger is not directly programmable; but it
is implemented as a class from which you can derive your own debugger
class, which you can make as fancy as you like.


Debugger commands
=================

($) statement
        Execute the (one-line) statement in the context of the current
        stack frame.  The exclamation point can be omitted unless the
        first word of the statement resembles a debugger command.  To
        assign to a global variable you must always prefix the command
        with a 'global' command, e.g.:
        (Pydb) global list_options; list_options = ['-l']
        (Pydb)

alias [name [command]]
        Creates an alias called 'name' that executes 'command'.  The
        command must *not* be enclosed in quotes.  Replaceable
        parameters can be indicated by %1, %2, and so on, while %* is
        replaced by all the parameters.  If no command is given, the
        current alias for name is shown. If no name is given, all
        aliases are listed.

        Aliases may be nested and can contain anything that can be
        legally typed at the pydb prompt.  Note!  You *can* override
        internal pydb commands with aliases!  Those internal commands
        are then hidden until the alias is removed.  Aliasing is
        recursively applied to the first word of the command line; all
        other words in the line are left alone.

        As an example, here are two useful aliases (especially when
        placed in the .pydbrc file):

        #Print instance variables (usage "pi classInst")
        alias pi for k in %1.__dict__.keys(): print "%1.",k,"=",%1.__dict__[k]
        #Print instance variables in self
        alias ps pi self


b(reak) [ ([filename:]lineno | function) [, condition] ]

	Without an argument, use the current point stopped in the
	program.

        With a filename:line number argument, set a break there.  If
        filename is omitted, use the current file.  With a function
        name, set a break at the first executable line of that
        function.

        Each breakpoint is assigned a number to which all the other
        breakpoint commands refer. Multiple breakpoints at one place
        are permitted, and useful with conditional arguments.

        The condition argument, if present, is a string which must
        evaluate to true in order for the breakpoint to be honored.

cd DIRECTORY

	Set working directory to DIRECTORY for debugger and program
	being debugged.

cl(ear) {[file:]linenumber | function}

       	Clear breakpoint at specified line or function.

       	Argument may be line number, function name, or "*" and an
	address.  If line number is specified, all breakpoints in that
	line are cleared.  If function is specified, breakpoints at
	beginning of function are cleared.  If an address is
	specified, breakpoints at what address are cleared.

        With no argument, clears all breakpoints in the line that the
        selected frame is executing in.

	See also the 'delete' command which clears breakpoints by number.

complete cmd-prefix
        Print a list of commands names that start with cmd-prefix.
	
	This is command is only availaible if readline supports it.

condition bpnumber condition
        condition is an expression which must evaluate to true before
        the breakpoint is honored.  If condition is absent, any
        existing condition is removed; i.e., the breakpoint is made
        unconditional.

c(ontinue)
        Continue execution, only stop when a breakpoint is encountered.

commands [bpnumber]
	>...
	>end
	(Pydb)

	Set commands to be executed when a breakpoint is hit.
	Give breakpoint number as the argument after "commands".
	With no bpnumber argument, commands refers to the last one set.
	The commands themselves follow starting on the next line.
	Type a line containing "end" to terminate the commands.

	To remove all commands from a breakpoint, type commands and
	follow it immediately with end; that is, give no commands.

	You can use breakpoint commands to start your program up
	again. Simply use the continue command, or step, or any other
	command that resumes execution.

	Specifying any command resuming execution (currently continue, step,
	next, return, jump, and quit) terminates the command list as if that
	command was immediately followed by 'end'.  This is because any time
	you resume execution (even with a simple next or step), you may
	encounter another breakpoint--which could have its own command list,
	leading to ambiguities about which list to execute.

	If you use the 'silent' command in the command list, the
	usual message about stopping at a breakpoint is not printed.
	This may be desirable for breakpoints that are to print a
	specific message and then continue.  If none of the other
	commands print anything, you see no sign that the breakpoint
	was reached.


delete [bpnumber [bpnumber...]]

        Delete some breakpoints.  Arguments are breakpoint numbers
        with spaces in between.  To delete all breakpoints, give no
        argument.  those breakpoints.  Without argument, clear all
        breaks (but first ask confirmation).

        See also the 'clear' command which clears breakpoints by
        line/file number..

disable bpnumber [bpnumber ...]
        Disables the breakpoints given as a space separated list of
        breakpoint numbers.  Disabling a breakpoint means it cannot
        cause the program to stop execution, but unlike clearing a
        breakpoint, it remains in the list of breakpoints and can be
        (re-)enabled.

disassemble [arg]
        With no argument disassemble at the current frame location.
        With a numeric argument, disassemble at the frame location at that
        line number. With a class, method, function or code argument
        disassemble that.

display [format] EXP
	Print value of expression EXP each time the program stops.
	FMT may be used before EXP and may be one of 'c' for char, 
	'x' for hex, 'o' for ocatl, 'f' for float or 's' for string.

	With no argument, display all currently requested auto-display
	expressions.  Use "undisplay" to cancel display requests previously
	made.

down [count]
        Move the current frame one level down in the stack trace
        (to a newer frame). With a count, which can be a positive
	or a negative value, move that many positions.

enable bpnumber [bpnumber ...]
        Enables the breakpoints specified.

examine expression
        Print the type of the expression and prettyprint its value.
	Alias is x (same as in Perl).
	
finish
        Continue execution until the current function returns.
	At that point the retval command can be used to show the
	return value.

frame position
	Move the current frame to the specified frame number. A negative
	number indicates position from the end, so "frame -1" moves to 
	the newest frame, and "frame 0" moves to the oldest frame.

h(elp)
        Without an argument, print the list of available commands.  With
        a command name as argument, print help about that command
        (this is currently not implemented).

ignore bpnumber count
        Sets the ignore count for the given breakpoint number.  If
        count is omitted, the ignore count is set to 0.  A breakpoint
        becomes active when the ignore count is zero.  When non-zero,
        the count is decremented each time the breakpoint is reached
        and the breakpoint is not disabled and any associated
        condition evaluates to true.

i(nfo) [suboption]
        In general, shows information about the program being debugged.
	Without argument, print the list of available info commands.
	With an argument, print info about that command. Suboptions follow:

	Without argument, print the list of available info commands.
	With an argument, print info about that command. Suboptions follow:

info args -- Argument variables of current stack frame
info break -- Status of user-settable breakpoints
info display -- Expressions to display when program stops,
                with code numbers.
info globals -- Global variables of current stack frame
info line -- Current line number in source file. If a function name is
               given the starting line of the function is reported.
info locals -- Local variables of current stack frame
info program -- Execution status of the program
info source -- Information about the current Python file

jump lineno
        Set the next line that will be executed.

l(ist) [- | first [last or count]]
        List source code. Without arguments, list LISTSIZE lines
        centered around the current line or continue the previous
        listing. "list -" lists LISTSIZE lines before a previous
        listing. With one argument other than "-", list LISTSIZE lines
        centered around the specified position.  With two arguments,
        list the given range; if the second argument is less than the
        first, it is a count.  First and last can be either a function
        name, a line number or file:line

n(ext) [count]
        Continue execution until the next line in the current function
        is reached or it returns. The difference between next and step
        is that step stops inside a called function, while next
        executes called functions at (nearly) full speed, only
        stopping at the next line in the current function.

p expression
        Print the value of the expression.

pp expression
        Prettyprint the value of the expression.

pwd
        Print working directory.

q(uit)
        Quit the debugger. The program being executed is aborted. For
	now, kill is a synonym 	for quit.

restart 
        Restart debugger and program via an exec call. All state
        is lost, and new copy of the debugger is used.

        Sometimes in debugging it is necessary to modify module code
        when one finds a bugs in them. Python will not notice
        dynamically that a module has changed and thus not reimport
        , so in such a situation one must use "restart" rather than
	"run".

return
        Make selected stack frame return to its caller. Control
        remains in the debugger, but when you continue execution will
        resume at the return statement found inside the subroutine or
        method.  At present we are only able to perform this if we are
        in a subroutine that has a 'return' statement in it.

	See also retval and finish.

retval
        Show the value that is to be returned from a function.
	This command is useful after a "finish" command or stepping just 
	after a "return" statement. To change the value, make an
	assignment to the variable __return__.
	
	The short command name is rv.

	See also finish and return.

run     [args...]

        Run (or restart the debugged python program. If a string is
	supplied that becomes the new command arguments.

	History, breakpoints, actions nd debugger options are
        preserved. ' R' is a short command alias for run. 

	Note that there may be situations where "run" doesn't have the
        effect you want and you may have to use "restart" instead. See
        restart for more info.


set *subcommand*
    In general sets the debugger environment.
    With a subcommand, this command modifies parts of the debugger
    environment.  You can see these environment settings with the
    "show" command.

  set args *arg*...
 
    Set argument list to give program being debugged when it is
    started. Follow this command with any number of args, to be passed
    to the program.  Set number of source lines debugger will list by
    default.

  set history filename
    Set the filename in which to record the command history

  set history save
    Set saving of the history record on exit

  set history size
    Set the size of the command history

  set linetrace {on|off}
    Set line execution tracing. If 'on', lines will be shown before they 
    are run.

  set linetrace delay *float*
    Set delay after listing a line. This only has an effect if linetrace
    is in effect. This is useful if tracing inside a GUI that is displaying
    the position in the source text. A value like 0.5 is probably sufficient.

  set listsize *int*
    Set number of source lines debugger will list by default.

  set logging on
  set logging off
  set logging file FILENAME
  set logging overwrite [on|off]
  set logging redirect [on|off]

  set prompt *string*
    Set debugger's prompt

show *subcommand* 

    Generic command for showing things about the debugger.

    show args -- Show argument list to give program being debugged when
	it is started

    show cmdtrace -- Show if we are to show debugger commands before running

    show commands -- Show the history of commands you typed. 
      This command Is available only if the readline module available
      and supports the history saving.

    show history -- Generic command for showing command history parameters

    show interactive -- Show if we are interactive or not

    show linetrace -- Show the line tracing status

    show listsize -- Show number of source lines gdb will list by
  	default

    show prompt -- Show the current debugger prompt

    show version -- Show what version of this is

source FILE
        Read commands from a file named FILE.
        Note that the file '.pydbrc' is read automatically
        in this way when pydb is started.

        An error in any command terminates execution of the command
        file and control is returned to the console.

	For tracking down problems with command files, see the "set
	cmdtrace on" debugger command.

s(tep) [count]
        Execute the current line, stop at the first possible occasion
        (either in a function that is called or in the current function).


tbreak  [ ([filename:]lineno | function) [, condition] ]
        Set a temporary breakpoint. Arguments are like the "break" command.
        Like "break" except the breakoint is only temporary, 
        so it will be deleted when hit.  
unalias name
        Deletes the specified alias.

undisplay 
        Cancel some expressions to be displayed when program stops.
        Arguments are the code numbers of the expressions to stop displaying.
        No argument means cancel all automatic-display expressions.
        "delete display" has the same effect as this command.
        Do "info display" to see current list of code numbers.

up [count]
        Move the current frame one level up in the stack trace
        (to an older frame). With a count, which can be a positive
	or a negative value, move that many positions.

whatis arg
         Prints the type of the argument.

where [count]
        Print a stack trace, with the most recent frame at the bottom.
	With a positive number, print at most many entries.
        An arrow indicates the "current frame", which determines the
        context of most commands. bt and T are short command names for 
	this.