23.3.1 Python Commands

GDB provides two commands for accessing the Python interpreter, and one related setting:

python-interactive [command]

pi [command]

Without an argument, the python-interactive command can be used to start an interactive Python prompt. To return to GDB, type the EOF character (e.g., Ctrl-D on an empty prompt).

Alternatively, a single-line Python command can be given as an argument and evaluated. If the command is an expression, the result will be printed; otherwise, nothing will be printed. For example:

(gdb) python-interactive 2 + 3
5

python [command]

py [command]

The python command can be used to evaluate Python code.

If given an argument, the python command will evaluate the argument as a Python command. For example:

(gdb) python print 23
23

If you do not provide an argument to python, it will act as a multi-line command, like define. In this case, the Python script is made up of subsequent command lines, given after the python command. This command list is terminated using a line containing end. For example:

(gdb) python
>print 23
>end
23

set python print-stack

By default, GDB will print only the message component of a Python exception when an error occurs in a Python script. This can be controlled using set python print-stack: if full, then full Python stack printing is enabled; if none, then Python stack and message printing is disabled; if message, the default, only the message component of the error is printed.

set python ignore-environment [on|off]

By default this option is ‘off’, and, when GDB initializes its internal Python interpreter, the Python interpreter will check the environment for variables that will effect how it behaves, for example PYTHONHOME, and PYTHONPATH¹⁸.

If this option is set to ‘on’ before Python is initialized then Python will ignore all such environment variables. As Python is initialized early during GDB’s startup process, then this option must be placed into the early initialization file (see Initialization Files) to have the desired effect.

This option is equivalent to passing -E to the real python executable.

set python dont-write-bytecode [auto|on|off]

When this option is ‘off’, then, once GDB has initialized the Python interpreter, the interpreter will byte-compile any Python modules that it imports and write the byte code to disk in .pyc files.

If this option is set to ‘on’ before Python is initialized then Python will no longer write the byte code to disk. As Python is initialized early during GDB’s startup process, then this option must be placed into the early initialization file (see Initialization Files) to have the desired effect.

By default this option is set to ‘auto’. In this mode, provided the python ignore-environment setting is ‘off’, the environment variable PYTHONDONTWRITEBYTECODE is examined to see if it should write out byte-code or not. PYTHONDONTWRITEBYTECODE is considered to be off/disabled either when set to the empty string or when the environment variable doesn’t exist. All other settings, including those which don’t seem to make sense, indicate that it’s on/enabled.

This option is equivalent to passing -B to the real python executable.

It is also possible to execute a Python script from the GDB interpreter:

source script-name

The script name must end with ‘.py’ and GDB must be configured to recognize the script language based on filename extension using the script-extension setting. See Extending GDB.

The following commands are intended to help debug GDB itself:

set debug py-breakpoint on|off

show debug py-breakpoint

When ‘on’, GDB prints debug messages related to the Python breakpoint API. This is ‘off’ by default.

set debug py-unwind on|off

show debug py-unwind

When ‘on’, GDB prints debug messages related to the Python unwinder API. This is ‘off’ by default.