Python Commands (Debugging with GDB)
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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 PYTHONPATH
19.
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 Python will check the environment variable PYTHONDONTWRITEBYTECODE
to see if it should write out byte-code or not.
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 thescript-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.
Footnotes
(19)
See the ENVIRONMENT VARIABLES section of man 1 python
for a comprehensive list.
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