The commands recognized by the debugger are listed below. Most commands can beabbreviated to one or two letters as indicated; e.g. h(elp) means thateither h or help can be used to enter the help command (but not heor hel, nor H or Help or HELP). Arguments to commands must beseparated by whitespace (spaces or tabs). Optional arguments are enclosed insquare brackets ([]) in the command syntax; the square brackets must not betyped. Alternatives in the command syntax are separated by a vertical bar(|).

Entering a blank line repeats the last command entered. Exception: if the lastcommand was a list command, the next 11 lines are listed.

Commands that the debugger doesn’t recognize are assumed to be Python statementsand are executed in the context of the program being debugged. Pythonstatements can also be prefixed with an exclamation point (!). This is apowerful way to inspect the program being debugged; it is even possible tochange a variable or call a function. When an exception occurs in such astatement, the exception name is printed but the debugger’s state is notchanged.

Changed in version 3.13: Expressions/Statements whose prefix is a pdb command are now correctlyidentified and executed.

The debugger supports aliases. Aliases can haveparameters which allows one a certain level of adaptability to the context underexamination.

Multiple commands may be entered on a single line, separated by ;;. (Asingle ; is not used as it is the separator for multiple commands in a linethat is passed to the Python parser.) No intelligence is applied to separatingthe commands; the input is split at the first ;; pair, even if it is in themiddle of a quoted string. A workaround for strings with double semicolonsis to use implicit string concatenation ';'';' or ";"";".

To set a temporary global variable, use a convenience variable. A conveniencevariable is a variable whose name starts with $. For example, $foo = 1sets a global variable $foo which you can use in the debugger session. Theconvenience variables are cleared when the program resumes execution so it’sless likely to interfere with your program compared to using normal variableslike foo = 1.

There are three preset convenience variables:

$_frame: the current frame you are debugging

$_retval: the return value if the frame is returning

$_exception: the exception if the frame is raising an exception

Added in version 3.12: Added the convenience variable feature.

If a file .pdbrc exists in the user’s home directory or in the currentdirectory, it is read with 'utf-8' encoding and executed as if it had beentyped at the debugger prompt, with the exception that empty lines and linesstarting with # are ignored. This is particularly useful for aliases. If bothfiles exist, the one in the home directory is read first and aliases defined therecan be overridden by the local file.

Changed in version 3.2: .pdbrc can now contain commands that continue debugging, such ascontinue or next. Previously, these commands had noeffect.

Changed in version 3.11: .pdbrc is now read with 'utf-8' encoding. Previously, it was readwith the system locale encoding.

Without argument, print the list of available commands. With a command asargument, print help about that command. help pdb displays the fulldocumentation (the docstring of the pdb module). Since the commandargument must be an identifier, help exec must be entered to get help onthe ! command.

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.

Move the current frame count (default one) levels down in the stack trace(to a newer frame).

Move the current frame count (default one) levels up in the stack trace (toan older frame).

With a lineno argument, set a break at line lineno in the current file.The line number may be prefixed with a filename and a colon,to specify a breakpoint in another file (possibly one that hasn’t been loadedyet). The file is searched on sys.path. Accepatable forms of filenameare /abspath/to/file.py, relpath/file.py, module andpackage.module.

With a function argument, set a break at the first executable statement withinthat function. function can be any expression that evaluates to a functionin the current namespace.

If a second argument is present, it is an expression which must evaluate totrue before the breakpoint is honored.

Without argument, list all breaks, including for each breakpoint, the numberof times that breakpoint has been hit, the current ignore count, and theassociated condition if any.

Each breakpoint is assigned a number to which all the otherbreakpoint commands refer.

Temporary breakpoint, which is removed automatically when it is first hit.The arguments are the same as for break.

With a filename:lineno argument, clear all the breakpoints at this line.With a space separated list of breakpoint numbers, clear those breakpoints.Without argument, clear all breaks (but first ask confirmation).

Disable the breakpoints given as a space separated list of breakpointnumbers. Disabling a breakpoint means it cannot cause the program to stopexecution, but unlike clearing a breakpoint, it remains in the list ofbreakpoints and can be (re-)enabled.

Enable the breakpoints specified.

Set 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 ignorecount is zero. When non-zero, the count is decremented each time thebreakpoint is reached and the breakpoint is not disabled and any associatedcondition evaluates to true.

Set a new condition for the breakpoint, an expression which must evaluateto true before the breakpoint is honored. If condition is absent, anyexisting condition is removed; i.e., the breakpoint is made unconditional.

Specify a list of commands for breakpoint number bpnumber. The commandsthemselves appear on the following lines. Type a line containing justend to terminate the commands. An example:

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

With no bpnumber argument, commands refers to the last breakpoint set.

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

Specifying any command resuming execution(currently continue, step, next,return, jump, quit and their abbreviations)terminates the command list (as ifthat command was immediately followed by end). This is because any time youresume execution (even with a simple next or step), you may encounter anotherbreakpoint—which could have its own command list, leading to ambiguities aboutwhich list to execute.

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

Execute the current line, stop at the first possible occasion (either in afunction that is called or on the next line in the current function).

Continue execution until the next line in the current function is reached orit returns. (The difference between next and step isthat step stops inside a called function, while nextexecutes called functions at (nearly) full speed, only stopping at the nextline in the current function.)

Without argument, continue execution until the line with a number greaterthan the current one is reached.

With lineno, continue execution until a line with a number greater orequal to lineno is reached. In both cases, also stop when the current framereturns.

Changed in version 3.2: Allow giving an explicit line number.

Continue execution until the current function returns.

Continue execution, only stop when a breakpoint is encountered.

Set the next line that will be executed. Only available in the bottom-mostframe. This lets you jump back and execute code again, or jump forward toskip code that you don’t want to run.

It should be noted that not all jumps are allowed – for instance it is notpossible to jump into the middle of a for loop or out of afinally clause.

List source code for the current file. Without arguments, list 11 linesaround the current line or continue the previous listing. With . asargument, list 11 lines around the current line. With one argument,list 11 lines around at that line. With two arguments, list the given range;if the second argument is less than the first, it is interpreted as a count.

The current line in the current frame is indicated by ->. If anexception is being debugged, the line where the exception was originallyraised or propagated is indicated by >>, if it differs from the currentline.

Changed in version 3.2: Added the >> marker.

List all source code for the current function or frame. Interesting linesare marked as for list.

Added in version 3.2.

Print the arguments of the current function and their current values.

Evaluate expression in the current context and print its value.

Note

print() can also be used, but is not a debugger command — this executes thePython print() function.

Like the p command, except the value of expression ispretty-printed using the pprint module.

Print the type of expression.

Try to get source code of expression and display it.

Added in version 3.2.

Display the value of expression if it changed, each time execution stopsin the current frame.

Without expression, list all display expressions for the current frame.

Note

Display evaluates expression and compares to the result of the previousevaluation of expression, so when the result is mutable, display may notbe able to pick up the changes.

Example:

Display won’t realize lst has been changed because the result of evaluationis modified in place by lst.append(1) before being compared:

You can do some tricks with copy mechanism to make it work:

Added in version 3.2.

Do not display expression anymore in the current frame. Withoutexpression, clear all display expressions for the current frame.

Added in version 3.2.

Start an interactive interpreter (using the code module) in a newglobal namespace initialised from the local and global namespaces for thecurrent scope. Use exit() or quit() to exit the interpreter andreturn to the debugger.

Note

As interact creates a new dedicated namespace for code execution,assignments to variables will not affect the original namespaces.However, modifications to any referenced mutable objects will be reflectedin the original namespaces as usual.

Added in version 3.2.

Changed in version 3.13: exit() and quit() can be used to exit the interactcommand.

Changed in version 3.13: interact directs its output to the debugger’soutput channel rather than sys.stderr.

Create an alias called name that executes command. The command mustnot be enclosed in quotes. Replaceable parameters can be indicated by%1, %2, … and %9, while %* is replaced by all the parameters.If command is omitted, the current alias for name is shown. If noarguments are given, all aliases are listed.

Aliases may be nested and can contain anything that can be legally typed atthe pdb prompt. Note that internal pdb commands can be overridden byaliases. Such a command is then hidden until the alias is removed. Aliasingis recursively applied to the first word of the command line; all other wordsin the line are left alone.

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

Delete the specified alias name.

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 statementresembles a debugger command, e.g.:

To set a global variable, you can prefix the assignment command with aglobal statement on the same line, e.g.:

Restart the debugged Python program. If args is supplied, it is splitwith shlex and the result is used as the new sys.argv.History, breakpoints, actions and debugger options are preserved.restart is an alias for run.

Quit from the debugger. The program being executed is aborted.

Enter a recursive debugger that steps through code(which is an arbitrary expression or statement to beexecuted in the current environment).

Print the return value for the last return of the current function.

List or jump between chained exceptions.

When using pdb.pm() or Pdb.post_mortem(...) with a chained exceptioninstead of a traceback, it allows the user to move between thechained exceptions using exceptions command to list exceptions, andexception to switch to that exception.

Example:

calling pdb.pm() will allow to move between exceptions:

Added in version 3.13.

Footnotes

Whether a frame is considered to originate in a certain moduleis determined by the __name__ in the frame globals.