it' possible you don' have any hugememory-consuming code that would benefit from the flyweight patternbut can you think of situations where it might be usefulanywhere that large amounts of overlapping data need to be processeda flyweight is waiting to be used would it be useful in the banking industryin web applicationsat what point does the flyweight pattern make sensewhen is it overkillwhat about the command patterncan you think of any common (or better yetuncommonexamples of places where the decoupling of action from invocation would be usefullook at the programs you use on daily basisand imagine how they are implemented internally it' likely that many of them use the command pattern for one purpose or another the abstract factory patternor the somewhat more pythonic derivatives we discussedcan be very useful for creating one-touch-configurable systems can you think of places where such systems are usefulfinallyconsider the composite pattern there are tree-like structures all around us in programmingsome of themlike our file hierarchy exampleare blatantothers are fairly subtle what situations might arise where the composite pattern would be usefulcan you think of places where you can use it in your own codewhat if you adapted the pattern slightlyfor exampleto contain different types of leaf or composite nodes for different types of objectssummary in this we went into detail on several more design patternscovering their canonical descriptions as well as alternatives for implementing them in pythonwhich is often more flexible and versatile than traditional object-oriented languages the adapter pattern is useful for matching interfaceswhile the facade pattern is suited to simplifying them flyweight is complicated pattern and only useful if memory optimization is required in pythonthe command pattern is often more aptly implemented using first class functions as callbacks abstract factories allow run-time separation of implementations depending on configuration or system information the composite pattern is used universally for tree-like structures in the next we'll discuss how important it is to test python programsand how to do it