Dynamic Typing Is Everywhere

Of course, you don’t really need to draw name/object diagrams with circles and arrows to use Python. When you’re starting out, though, it sometimes helps you understand unusual cases if you can trace their reference structures. If a mutable object changes out from under you when passed around your program, for example, chances are you are witnessing some of this chapter’s subject matter firsthand.

Moreover, even if dynamic typing seems a little abstract at this point, you probably will care about it eventually. Because everything seems to work by assignment and references in Python, a basic understanding of this model is useful in many different contexts. As you’ll see, it works the same in assignment statements, function arguments, for loop variables, module imports, class attributes, and more. The good news is that there is just one assignment model in Python; once you get a handle on dynamic typing, you’ll find that it works the same everywhere in the language.

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At the most practical level, dynamic typing means there is less code for you to write. Just as importantly, though, dynamic typing is also the root of Python’s polymorphism, a concept we introduced in Chapter 4 and will revisit again later in this book. Because we do not constrain types in Python code, it is highly flexible. As you’ll see, when used well, dynamic typing and the polymorphism it provides produce code that automatically adapts to new requirements as your systems evolve.