Java vs. Python: What are the Differences?

shutterstock_124888153Java and Python are both great choices for the beginner programmer. This much you might already know, but when it comes to picking one and sticking with it… how do you decide? There are many things that might sway your preferences when it comes to choosing a language. Learn some of the primary differences here!

No matter which language you choose, get a head start on some coding fundamentals with this introduction to programming course.

Building and Running

The biggest difference between Java and Python, arguably, is how both languages are built and run.

Java

Once your code is ready in Java, you need to compile it into Java Bytecode. The build output (or the artifact) of your code comes in the form of .class files, which mirror the .java files that you originally had. You can also build your project as a .jar file, or a Java executable that conveniently packages up your .class files.

Just trying to run your original .java files won’t do you much good, since they need to be compiled. Once you have your directory of .class files or your .jar file, you need a Java Virtual Machine to run it. If you’ve ever tried to run a Java program without Java Runtime Environment (JRE), that’s the reason your computer will call for its installation.

So in a nutshell, Java code needs to be compiled into Java Bytecode in the form of either .class files or .jar files using a Java Compiler, then the artifacts need to be run on a Java Virtual Machine – a lot of steps for setting up your program. Get an introduction to Java programming with this course.

Python

Python, on the other hand, is a scripting language. When you code a .py file, you don’t need to compile the code before running it. For Python, and other scripting languages as well, you need an interpreter to run your code. You can download Python’s interpreter from its official website, and learn how to setup your first Python project with this introduction to Python course.

When you launch the Python interpreter, it will display a prompt where you can input lines of Python code, and present results for each line. While you can compile Python into .pyc files, which allows the interpreter to run your program more efficiently, you aren’t required to build your project. Once you code something in Python, you just need to run the interpreter with your .py file, and that’s it!

Learn the true differences between an interpreter and a compiler in this guide.

Typing

Another difference is in the way both languages are typed. In short, Java is statically typed, while Python is dynamically typed. Find out more below, or learn some coding basics with this course.

Java

In Java, when you create an object, you always need to specify its type. For example, let’s say we want to create an integer and a String type – you must explicitly state the type for each one:

int var1 = 10
String var2 = "Hello World";

Once variables in Java have been initialized, they cannot be assigned any other value that doesn’t match their original value. Going off the example above, var1 – an integer – can never be assigned a String like “Hello World.” This might seem restrictive on some levels, but on the other hand, your code is naturally less prone to errors, since any typos or mistakes will be caught when the code is compiling. Check out this beginner’s Java programming course for more tips.

Python

Variables in Python are dynamically typed, meaning any variable can take on any type. It doesn’t matter. For example:

x = 10 + 12
x = "Hello World"

The above statements are totally legal in Python. The reason for this is Python’s interpreter, which reads in and handles variables as they come. Because your code is interpreted, it doesn’t have the necessary typing checks that Java would have. This lack of restriction can be pretty convenient, but accidentally using variables as the wrong type can also cause a lot of issues while you’re program is running, so it’s a trade-off. Check out this ultimate Python programming tutorial for beginners for more info.

Syntax

Though they follow a lot of traditional computer programming structure and paradigms, Java and Python are completely different languages with different syntax. One of the most noticeable ones is how each language creates start and end blocks for class declarations, functions, if statements, while statements, and so on.

Java

Java uses curly brackets for start and end blocks, like so:

     class SimpleJavaClass {
          int var1;

          public SimpleJavaClass() {
               var1  = 0;
          }

          public void addToVar(int x) {
               var1 = var1 + x;
          }
     }

Since the curly brackets above encapsulate our blocks, we don’t actually need to have the nice spacing you see above. In fact, this whole Java class could exist on one line and it would be perfectly legal in the code. (But it would look really ugly!)

For more help with programming syntax, check out this course on the structure and interpretation of computer science.

Python

That isn’t the case for Python, which uses indentation for its code blocks. Here’s the same class above, but coded in Python instead:

     class SimplePythonClass:
          var1 = 0

          def addToVar(x):
               var1 = var1 + x

There are quite a few differences here, but the biggest is the lack of curly brackets. Because indentation is required for code blocks, we know that any code indented in a single tab or more than the class declaration is part of that class. Same goes for functions, if statements, etc. Not only does this make the code look cleaner, but it also enforces good visual structure in your code, for readability.

Minor Syntax Differences

Other minor differences include the use of semicolons at the end of statements.

Java:

     int x = 10;
     int y = 20;

Python:

     x = 10
     y = 20

The use of parentheses for if, else, while, and for statements.

Java:

     if (x > 5) { }

Python:

     if x > 5:

Check out this Python training course for more programming tutorials, or if you’ve decided Java is more your thing, here’s a course on Java programming for complete beginners.