Dynamic Typing vs. Static Typing: What’s The Difference?

Programming languages differ in how they identify and treat different data types, like numbers or words. You can think of data types as labels that tell your computer what type of information you have. For example, the number “30” requires different handling than the word “hello.”

The two main ways of processing data labels and types are “dynamic typing” and “static typing.” Whether your programming uses dynamic or static typing will depend on when it expects you to assign a label to your variable, and how strict this label is. To grasp this concept in greater depth, consider what each is, how it’s used, and why you might choose to use it.

What is static typing?

Static typing is a way of programming where you declare the type of data your variable uses before you assign a value. For example, in Java (a statically typed language) you could say in Java:

int weight = 30;

In this line of code, you are defining “weight” as an integer, or whole number, by putting “int” before it. The “30” assigns a value of 30. If you later wrote: 

weight = “hello”; 

You would get an error because you had previously defined “weight” as an integer, and could not suddenly assign it a string (or word) value. This approach makes your programs more predictable and helps you catch errors early, which can help you optimize your program’s performance. It also promotes clearer code and documentation, helping you and your collaborators easily keep track of your variable types and the data referenced within your code.

What is static typing used for?

Static typing is commonly used for large-scale development projects where you’re prioritizing safety, reliability, and performance. This is because statically-typed languages help you catch errors quickly and early, making it a more secure choice with a clearer code structure. 

You might choose statically-typed languages, such as Java and C++, when you’re working with multiple developers or need to share your code with a team. By clearly defining the type of every variable and function, the code becomes more readable and easier to understand. It also helps prevent accidental errors. For example, if you build an application that provides you with a list of your subscription services (a list of strings), and a developer on your team mistakenly tries to return the number of subscription services (an integer), the compiler will flag the mismatch right away before it reaches your users.

Static typing also plays a major role in “performance-critical” applications, such as in medicine or aerospace, where even a small mistake can have serious consequences. Using static typing can help catch mistakes before they cause harm. For example, a hospital management system written in Java might store patient doses numerically. If someone tried to assign “twenty” to this variable instead of the number “20,” you would get an error immediately. This kind of strict type enforcement helps reduce the risk of dangerous input errors and ensures that developers handle sensitive data precisely and consistently. 

Advantages of static typing

Static typing offers early error detection, which is one of the most important advantages for these types of languages, especially when working on large-scale or long-term projects. Because the compiler checks all variables before the code runs, you can catch bugs in your code during development rather than during testing or production. This adds a layer of reliability and safety that can improve the performance of your development. 

In addition to this, many static languages offer more support through available tools, such as autocompletion. Refactoring your code is also easier with statically-typed language, which is a process where you restructure and improve your code without changing its function. With static typing, you ensure your variable types remain consistent throughout code changes, increasing the safety and efficiency of this restructuring process.

Disadvantages of static typing

Like any code type, static typing has disadvantages. It requires more upfront code and variable declarations, which can slow the prototyping process and increase the learning curve for new developers. It also reduces flexibility and may feel rigid or restrictive in some environments. 

What is dynamic typing?

Dynamic typing is a way of programming where the programming language decides what each type of variable is while the program runs, rather than before it starts. This means that the computer figures out what type of data you’re working with as it goes. Instead of defining your variable types directly (e.g., string, number, character), the program keeps track of variable types as you assign them. For example, you might start by writing in Python:

weight = 30

This has assigned your variable “weight” to be an integer valued at 30. If you then type:

weight = “amount”

You have now reassigned weight to be a string value, and the computer will treat it as such. This type of assignment makes the code easier and faster to write, which is why you might choose it to perform quick tests, scripts, or if you have changing data.

What is dynamic typing used for?

Dynamic typing is used for situations where you are prototyping or developing in a way that benefits from quick iterations, especially when your data types change during runtime. Dynamic languages, such as JavaScript and Python, excel in applications that require quick adjustments and responsiveness to real-world scenarios. Areas you might see this in particular include:

• Web development: Dynamic typing's flexibility allows you to quickly adjust websites, prototype and develop interactive applications, and respond in real time as the online space evolves. 

• Scientific computing: Python has increased in popularity in the research space in part because it allows scientists to quickly manipulate their data and perform complex calculations without excessive restrictions on their variables.

• Scripting and automation: For small scripts that serve to automate repetitive tasks, dynamic typing makes it easier to develop and modify your code quickly. 

Advantages of dynamic typing

Dynamic typing makes it easier for you to write and modify code quickly. This can lead to faster development cycles and more flexibility, especially if you are a beginner or you are experimenting with new ideas. This set-up leads to advantages such as:

• Concise and easier-to-write code: Having fewer declarations means you can write fewer lines for your projects.

• Flexible variable usage: The same variable can take on different data types throughout your code without errors.

• Faster iterations: You can quickly write and test code ideas without needing to define everything upfront.

Disadvantages of dynamic typing

The flexibility of dynamic coding comes with trade-offs. Because you aren’t checking your variables automatically for type consistency until the program runs, you can have errors that go unnoticed throughout your development process. You may need to spend more time and attention to debugging and performance, especially as your projects grow. If you’re working with big data sets or teams, adding clear documentation and consistent communication can help keep your code organized and avoid confusion among team members.

Dynamic vs. static typing: When to use each

In general, if your priorities are to avoid errors at all costs, develop a program with a strong foundation, and avoid unpredictable behavior, go with static typing. If you are looking to explore new ideas, embrace real-world data, and rapidly iterate, dynamic typing is for you. For a quick overview of the main differences, consider the following table.

Learn programming with Coursera

Static typing requires you to assign your data types upfront, while dynamic typing allows more flexibility as you go. Understanding this distinction–and when to use each type–is an important step in building a strong foundation in computer programming. On Coursera, you can take exciting courses in both static and dynamically-typed programs. 

To begin, consider the IBM Full Stack Software Developer Professional Certificate, where you can learn how to develop with front-end development languages and tools such as HTML, CSS, JavaScript, React, and Bootstrap. You’ll also have the chance to explore program applications using back-end languages and frameworks like Express, Node.js, Python, and Django, expanding your toolkit to a diverse set of languages.