py-break

py.py

class PyNameEquals(gdb.Function):

    def __init__(self):
        gdb.Function.__init__ (self,
                              "pyname_equals")

    def _get_pycurframe_attr(self, attr):
        frame = Frame(gdb.selected_frame())
        if frame.is_evalframeex():
            pyframe = frame.get_pyop()
            if pyframe is None:
                warnings.warn("Use a Python debug build, Python breakpoints "
                              "won't work otherwise.")
                return None

            return getattr(pyframe, attr).proxyval(set())

        return None

    def invoke(self, funcname):
        attr = self._get_pycurframe_attr('co_name')
        return attr is not None and attr == funcname.string()

PyNameEquals()

class PyModEquals(PyNameEquals):

    def __init__(self):
        gdb.Function.__init__ (self,
                              "pymod_equals")

    def invoke(self, modname):
        attr = self._get_pycurframe_attr('co_filename')
        if attr is not None:
            filename, ext = os.path.splitext(os.path.basename(attr))
            return filename == modname.string()
        return False

PyModEquals()

class PyBreak(gdb.Command):
    """
    Set a Python breakpoint. Examples:
    Break on any function or method named 'func' in module 'modname'
        py-break modname.func
    Break on any function or method named 'func'
        py-break func
    """
    def __init__(self):
        gdb.Command.__init__ (self,
                              "py-break",
                              gdb.COMMAND_RUNNING,
                              gdb.COMPLETE_NONE)

    def invoke(self, funcname, from_tty):
        if '.' in funcname:
            modname, dot, funcname = funcname.rpartition('.')
            cond = '$pyname_equals("%s") && $pymod_equals("%s")' % (funcname,
                                                                    modname)
        else:
            cond = '$pyname_equals("%s")' % funcname

        gdb.execute('break PyEval_EvalFrameEx if ' + cond)

PyBreak()

Add to libpython.py and install python3-dbg.