Online doc for writing mi commands in python.

    https://sourceware.org/gdb/current/onlinedocs/gdb.html/GDB_002fMI-Commands-In-Python.html#GDB_002fMI-Commands-In-Python

The following code snippet shows how some trivial MI commands can be implemented in Python:

    class MIEcho(gdb.MICommand):
        """Echo arguments passed to the command."""

        def __init__(self, name, mode):
            self._mode = mode
            super(MIEcho, self).__init__(name)

        def invoke(self, argv):
            if self._mode == 'dict':
                return { 'dict': { 'argv' : argv } }
            elif self._mode == 'list':
                return { 'list': argv }
            else:
                return { 'string': ", ".join(argv) }


    MIEcho("-echo-dict", "dict")
    MIEcho("-echo-list", "list")
    MIEcho("-echo-string", "string")

The last three lines instantiate the class three times, creating three new GDB/MI commands -echo-dict, -echo-list, and -echo-string. Each time a subclass of gdb.MICommand is instantiated, the new command is automatically registered with GDB.

Source the py file at the gdb prompt.

    (gdb) source MIEcho.py

    Depending on how the Python code is read into GDB, you may need to import the gdb module explicitly.

The following example shows a GDB session in which the above commands have been added:

    (gdb)
    -echo-dict abc def ghi
    ^done,dict={argv=["abc","def","ghi"]}
    (gdb)
    -echo-list abc def ghi
    ^done,list=["abc","def","ghi"]
    (gdb)
    -echo-string abc def ghi
    ^done,string="abc, def, ghi"
    (gdb)



Here's a simple non-MI command added with python to gdb.

    class HelloWorld (gdb.Command):

    """Greet the whole world."""

    def __init__ (self):
        super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)

    def invoke (self, arg, from_tty):
        print ("Hello, World!")

    HelloWorld ()

Put it in a .py file and load it in gdb.

    (gdb) source HelloWorld.py

Then execute it.

    (gdb) hello-world
    Hello, World!