Defining Options¶

So far we have concerned ourselves with whom we greet and not with how, let us change. How an application does things can usually be changed by using options, unfortunately there is not much you can change when saying hello to someone, so we are going to turn our application into something much more general, that is an application that greets people:

@application.option('--greeting greeting')
def greeting(context, greeting):
    context['greeting'] = greeting

This is quite similar to how main functions are defined. The difference is that the signature in case of an option, includes the name of an option.

Another thing we do is use the context object that we have ignored so far. This object is basically a dictionary that is passed around to capture the state of the application. You are supposed to use it to store information gathered in options.

Now we can use this information in the context in a main function:

@application.main('[name...]')
def main(context, name=None):
    if name is None:
        name = [u'World']
    greeting = context.get('greeting', u'Hello')
    if len(name) == 1:
        print(u'%s, %s!' % (greeting, name[0]))
    elif len(name) == 2:
        print(u'%s %s and %s!' % (greeting, name[0], name[1]))
    else:
        print(u'%s %s and %s!' % (greeting, u', '.join(name[:-1]), name[-1]))

Now we can use the –greeting option to change the way our application greets people:

$ python hello.py --greeting Hi
Hi, World!

Continue with Defining Commands.