model-view-controller pattern alwaysworlds within worlds --clive barkerweaveworld not far along in your journey as programmeryou begin to see some other patterns emerge--more like patterns of patterns like this one most if not all programs consist of some sort of external action that initiates the program the initiating action may or may not have databut if it doesthe program consumes that datasometimes persisting itsometimes not finallyyour program has an effect on the world that' itbasicallyall programs you will ever encounter will have this pattern let me give you simple example and then one that you might not see from the start the first example is that of visitor signing up to receive email updates from website it does not matter how the user enters the informationas from the system' perspective everything begins with post request hitting the program the request contains name and email address now the program is initiated as in the preceding exampleand we have some extra data the program goes through the process of checking if the email is already in the database if notit is persisted together with the name of the visitor if it isthen no further action is taken finallythe system returns status code alerting the calling program that everything went as expected note that there are two places where the program changes the world outside of the execution of the program itselfnamely the database and the response to the calling system we could also look at gamewhere you have the game in some state and the player interacts with the game via the keyboard and mouse these peripheral actions are translated into commands by the game enginethe commands are processedand the game state updateswhich is relayed back to the player in terms of visualaudioand possible tactile feedback the process remains the sameinputprocessoutput (cwessel badenhorst badenhorstpractical python design patterns