Primer on Python Decorators – Real Python

Closure and recursion are powerful programming techniques that form the basis of a paradigm known as functional programming. Most people will find functional programming more difficult to understand than an approach based on for loops, if statements, variables, and simple functions.

Functional patterns can be simple or they can combine to create more complex patterns.

The Gang of Four stated two principles of good object-oriented design that were present in all the patterns: “favor object composition over class inheritance” and “program to an interface, not an implementation.”8

The instance variable enables individual objects to remember state. Instance variables work much like other variables: you assign values to them, and you read those values back; you can add them together, print them out, and so on. But instance variables have a few differences: Instance variable names always start with a single @ (at sign). This en

Blocks and procs are definitely some of the coolest features of Ruby. Some other languages have this feature, though they may call it something else (like closures or lambdas), but many don’t, and it’s a shame. They are a joy to use.

You can also write your own classes. You can even modify existing Ruby classes; if you don’t like the behavior of strings or arrays, you can change it. It’s almost always a bad idea to do so, but Ruby allows it.