— Function: Parameter.__init__ (name, command-class, parameter-class [, enum-sequence])

The object initializer for Parameter registers the new parameter with gdb. This initializer is normally invoked from the subclass' own __init__ method.

name is the name of the new parameter. If name consists of multiple words, then the initial words are looked for as prefix parameters. An example of this can be illustrated with the set print set of parameters. If name is print foo, then print will be searched as the prefix parameter. In this case the parameter can subsequently be accessed in gdb as set print foo.

If name consists of multiple words, and no prefix parameter group can be found, an exception is raised.

command-class should be one of the ‘COMMAND_’ constants (see Commands In Python). This argument tells gdb how to categorize the new parameter in the help system.

parameter-class should be one of the ‘PARAM_’ constants defined below. This argument tells gdb the type of the new parameter; this information is used for input validation and completion.

If parameter-class is PARAM_ENUM, then enum-sequence must be a sequence of strings. These strings represent the possible values for the parameter.

If parameter-class is not PARAM_ENUM, then the presence of a fourth argument will cause an exception to be thrown.

The help text for the new parameter is taken from the Python documentation string for the parameter's class, if there is one. If there is no documentation string, a default value is used.

— Variable: Parameter.set_doc

If this attribute exists, and is a string, then its value is used as the help text for this parameter's set command. The value is examined when Parameter.__init__ is invoked; subsequent changes have no effect.

— Variable: Parameter.show_doc

If this attribute exists, and is a string, then its value is used as the help text for this parameter's show command. The value is examined when Parameter.__init__ is invoked; subsequent changes have no effect.

— Variable: Parameter.value

The value attribute holds the underlying value of the parameter. It can be read and assigned to just as any other attribute. gdb does validation when assignments are made.

— Function: Parameter.get_set_string (self)

If this method exists, gdb will call it when a parameter's value has been changed via the set API (for example, set foo off). The value attribute has already been populated with the new value and may be used in output. This method must return a string. If the returned string is not empty, gdb will present it to the user.

If this method raises the gdb.GdbError exception (see Exception Handling), then gdb will print the exception's string and the set command will fail. Note, however, that the value attribute will not be reset in this case. So, if your parameter must validate values, it should store the old value internally and reset the exposed value, like so:

          class ExampleParam (gdb.Parameter):
             def __init__ (self, name):
                super (ExampleParam, self).__init__ (name,
                             gdb.COMMAND_DATA,
                             gdb.PARAM_BOOLEAN)
                self.value = True
                self.saved_value = True
             def validate(self):
                return False
             def get_set_string (self):
                if not self.validate():
                  self.value = self.saved_value
                  raise gdb.GdbError('Failed to validate')
                self.saved_value = self.value

— Function: Parameter.get_show_string (self, svalue)

gdb will call this method when a parameter's show API has been invoked (for example, show foo). The argument svalue receives the string representation of the current value. This method must return a string.