facade pattern the phantom of the opera is thereinside my mind --christine in this we will look at another way to hide the complexity of system from the users of that system all the moving parts should look like single entity to the outside world all systems are more complex than they seem at first glance takefor instancea point of sale (possystem most people only ever interact with such system as customer on the other side of the register in simple caseevery transaction that takes place requires number of things to happen the sale needs to be recordedthe stock levels for each item in the transaction need to be adjustedand you might even have to apply some sort of loyalty points for regular customers most of these systems also allow for specials that take into account the items in the transactionlike buy two and get the cheapest one for free point of sale example there are number of things involved in this transaction processthings like the loyalty systemthe stock systemspecials or promotions systemany payment systemsand whatever else is needed to make the process flow the way it should for each of these interactionswe will have different classes providing the functionality in question (cwessel badenhorst badenhorstpractical python design patterns