###
14.3.2.3 Handling boolean (flag) options

Flag options--set a variable to true or false when a particular option is seen--are quite common. `optparse` supports them with two separate actions, `store_true` and `store_false`. For example, you might have a `verbose` flag that is turned on with `"-v"` and off with `"-q"`:

    parser.add_option("-v", action="store_true", dest="verbose")
    parser.add_option("-q", action="store_false", dest="verbose")

Here we have two different options with the same destination, which is perfectly OK. (It just means you have to be a bit careful when setting default values--see below.)

When `optparse` encounters `"-v"` on the command line, it sets `options.verbose` to `True`; when it encounters `"-q"`, `options.verbose` is set to `False`.