Creating a basic “Hello World!”-Application¶
The first step on our journey will be to create a simple “Hello World!” application. The first part of that application consists of importing what we need:
from argvard import Argvard
The Argvard object is central to every Argvard application and – for now – the only thing we are going to need. The next part of the application is creating such an object:
application = Argvard()
As you can see this is trivial as we do not have to pass it any arguments. As you can see from the name I gave it, for all intents and purposes it is the application. The next step is making that the application do something:
@application.main() def main(context): print(u'Hello, World!')
The application.main decorator is used to register what in Argvard terms is called the main function. If you are familiar with other programming languages, you may be aware that a main function of some form can be found in many languages. In languages in which it exists it acts as an entry point and is automatically called when your application is started.
This case is similiar, main is a function that will always be called by the application after any options have been parsed. The main function is supposed to do, whatever your application is supposed to do.
The last step is calling the application:
if __name__ == '__main__': application()
If you are not already familiar with the pattern, __name__ is a special variable the interpreter sets to the name of the current module. If the module is being executed directly (and is not just imported), __name__ will be set to '__main__'. This ensures that application is not called, unless the module is executed directly, which makes it possible to import the module without any side effects.
Once you have typed that into your editor, save it as hello.py and execute it with python hello.py. It should print “Hello, World!” and exit.
Continue with Dealing with positional arguments.