Python vs Java

What is Python?

Python is an interpreted, object-oriented, high-level programming language with dynamic semantics. It’s high-level built-in data structures, combined with dynamic typing and dynamic binding, make it very attractive for Rapid Application Development, as well as for use as a scripting or glue language to connect existing components together. Python’s simple, easy to learn syntax emphasizes readability and therefore reduces the cost of program maintenance. Python supports modules and packages, which encourages program modularity and code reuse. The Python interpreter and the extensive standard library are available in source or binary form without charge for all major platforms, and can be freely distributed.

Often, programmers fall in love with Python because of the increased productivity it provides. Since there is no compilation step, the edit-test-debug cycle is incredibly fast. Debugging Python programs is easy: a bug or bad input will never cause a segmentation fault. Instead, when the interpreter discovers an error, it raises an exception. When the program doesn’t catch the exception, the interpreter prints a stack trace. A source-level debugger allows inspection of local and global variables, evaluation of arbitrary expressions, setting breakpoints, stepping through the code a line at a time, and so on. The debugger is written in Python itself, testifying to Python’s introspective power. On the other hand, often the quickest way to debug a program is to add a few print statements to the source: the fast edit-test-debug cycle makes this simple approach very effective.

See also some comparisons between Python and other languages.

Basic usage

The standard packaging tools are all designed to be used from the command line.

The following command will install the latest version of a module and its dependencies from the Python Packaging Index:

python -m pip install SomePackage

Note

For POSIX users (including Mac OS X and Linux users), the examples in this guide assume the use of a virtual environment.

For Windows users, the examples in this guide assume that the option to adjust the system PATH environment variable was selected when installing Python.

It’s also possible to specify an exact or minimum version directly on the command line. When using comparator operators such as >, < or some other special character which gets interpreted by the shell, the package name and the version should be enclosed within double quotes:

python -m pip install SomePackage==1.0.4    # specific version
python -m pip install "SomePackage>=1.0.4"  # minimum version

Normally, if a suitable module is already installed, attempting to install it again will have no effect. Upgrading existing modules must be requested explicitly:

python -m pip install --upgrade SomePackage

More information and resources regarding pip and its capabilities can be found in the Python Packaging User Guide.

Creation of virtual environments is done through the venv module. Installing packages into an active virtual environment uses the commands shown above.

How do I …?

These are quick answers or links for some common tasks.

… install pip in versions of Python prior to Python 3.4?

Python only started bundling pip with Python 3.4. For earlier versions, pip needs to be “bootstrapped” as described in the Python Packaging User Guide.

… install packages just for the current user?

Passing the --user option to python -m pip install will install a package just for the current user, rather than for all users of the system.

… install scientific Python packages?

A number of scientific Python packages have complex binary dependencies, and aren’t currently easy to install using pip directly. At this point in time, it will often be easier for users to install these packages by other means rather than attempting to install them with pip.

… work with multiple versions of Python installed in parallel?

On Linux, Mac OS X, and other POSIX systems, use the versioned Python commands in combination with the -m switch to run the appropriate copy of pip:

python2   -m pip install SomePackage  # default Python 2
python2.7 -m pip install SomePackage  # specifically Python 2.7
python3   -m pip install SomePackage  # default Python 3
python3.4 -m pip install SomePackage  # specifically Python 3.4

Appropriately versioned pip commands may also be available.

On Windows, use the py Python launcher in combination with the -m switch:

py -2   -m pip install SomePackage  # default Python 2
py -2.7 -m pip install SomePackage  # specifically Python 2.7
py -3   -m pip install SomePackage  # default Python 3
py -3.4 -m pip install SomePackage  # specifically Python 3.4

Common installation issues

Installing into the system Python on Linux

On Linux systems, a Python installation will typically be included as part of the distribution. Installing into this Python installation requires root access to the system, and may interfere with the operation of the system package manager and other components of the system if a component is unexpectedly upgraded using pip.

On such systems, it is often better to use a virtual environment or a per-user installation when installing packages with pip.

Pip not installed

It is possible that pip does not get installed by default. One potential fix is:

python -m ensurepip --default-pip

There are also additional resources for installing pip.

Installing binary extensions

Python has typically relied heavily on source-based distribution, with end-users being expected to compile extension modules from source as part of the installation process.

With the introduction of support for the binary wheel format, and the ability to publish wheels for at least Windows and Mac OS X through the Python Packaging Index, this problem is expected to diminish over time, as users are more regularly able to install pre-built extensions rather than needing to build them themselves.

Some of the solutions for installing scientific software that are not yet available as pre-built wheel files may also help with obtaining other binary extensions without needing to build them locally.

Hello, World!

Python is a very simple language and has a very straightforward syntax. It encourages programmers to program without boilerplate (prepared) code. The simplest directive in Python is the “print” directive – it simply prints out a line (and also includes a newline, unlike in C).

There are two major Python versions, Python 2 and Python 3. Python 2 and 3 are quite different. This tutorial uses Python 3 because it more semantically correct and supports newer features.

For example, one difference between Python 2 and 3 is the print statement. In Python 2, the “print” statement is not a function, and therefore it is invoked without parentheses. However, in Python 3, it is a function, and must be invoked with parentheses.

To print a string in Python 3, just write:

print("Hello, World!")

You can just as easily store a string as a variable and then print it to stdout:

my_string = "Hello, World!"
print(my_string)

The above code will print Hello, World! on your screen. Try it yourself in the editor below!

Input Format

You do not need to read any input in this challenge.

Output Format

Print Hello, World! to stdout.

Sample Output:
Hello, World!

 

What is Java? Executive Summary

Java produces applets (browser-run programs), which facilitate graphical user interface (GUI) and object interaction by Internet users. Prior to Java applets, Web pages were typically static and non-interactive. Java applets have diminished in popularity with the release of competing products, such as Adobe Flash and Microsoft Silverlight.

Java applets run in a Web browser with Java Virtual Machine (JVM), which translates Java bytecode into native processor instructions and allows indirect OS or platform program execution. JVM provides the majority of components needed to run bytecode, which is usually smaller than executable programs written through other programming languages. Bytecode cannot run if a system lacks required JVM.

Java program development requires a Java software development kit (SDK) that typically includes a compiler, interpreter, documentation generator and other tools used to produce a complete application.

Development time may be accelerated through the use of integrated development environments (IDE) – such as JBuilder, Netbeans, Eclipse or JCreator. IDEs facilitate the development of GUIs, which include buttons, text boxes, panels, frames, scrollbars and other objects via drag-and-drop and point-and-click actions.

Java programs are found in desktops, servers, mobile devices, smart cards and Blu-ray Discs (BD).

 

 

What is Java used for?

Before I answer the question, what is Java used for, let me brief you about why you should choose Java. Java is highly popular and has dominated this field from early 2000’s till the present 2018. 

Java has been used in different domains. Some of them are listed below:

  • Banking: To deal with transaction management.
  • Retail: Billing applications that you see in a store/restaurant are completely written in Java.
  • Information Technology: Java is designed to solve implementation dependencies.
  • Android: Applications are either written in Java or use Java API.
  • Financial services: It is used in server-side applications.
  • Stock market: To write algorithms as to which company they should invest in.  
  • Big Data: Hadoop MapReduce framework is written using Java.
  • Scientific and Research Community: To deal with huge amount of data.               

Beginning Java programming with Hello World Example

The process of Java programming can be simplified into three steps:

  • Create the program by typing it into a text editor and saving it to a file – HelloWorld.java.
  • Compile it by typing “javac HelloWorld.java” in the terminal window.
  • Execute (or run) it by typing “java HelloWorld” in the terminal window.

 

Below given program is the simplest program of Java printing “Hello World” to the screen. Let us try to understand every bit of code step by step.

/* This is a simple Java program.
FileName : "HelloWorld.java". */
class HelloWorld
{
// Your program begins with a call to main().
// Prints "Hello, World" to the terminal window.
public static void main(String args[])
{
System.out.println("Hello, World");
}
}

Output:

Hello, World

The “Hello World!” program consists of three primary components: the HelloWorld class definition, the method main and source code comments. Following explanation will provide you with a basic understanding of the code:

  1. Class definition: This line uses the keyword class to declare that a new class is being defined.
    class HelloWorld 
    

    HelloWorld is an identifier that is the name of the class. The entire class definition, including all of its members, will be between the opening curly brace  {  and the closing curly brace } .

  2. main method: In Java programming language, every application must contain a main method whose signature is:
    public static void main(String[] args)
    
    public: So that JVM can execute the method from anywhere.
    static: Main method is to be called without object. 
    The modifiers public and static can be written in either order.
    void: The main method doesn't return anything.
    main(): Name configured in the JVM.
    String[]: The main method accepts a single argument: 
              an array of elements of type String.

    Like in C/C++, main method is the entry point for your application and will subsequently invoke all the other methods required by your program.

  3. The next line of code is shown here. Notice that it occurs inside main( ).
    System.out.println("Hello, World");
    

    T his line outputs the string “Hello, World” followed by a new line on the screen. Output is actually accomplished by the built-in println( ) method. System is a predefined class that provides access to the system, and out is the variable of type output stream that is connected to the console.

  4. Comments: They can either be multi-line or single-line comments.
    /* This is a simple Java program. 
    Call this file "HelloWorld.java". */
    

    This is a multiline comment. This type of comment must begin with /* and end with */. For a single line, you may directly use // as in C/C++.

Important Points :

  • The name of the class defined by the program is HelloWorld, which is same as the name of the file(HelloWorld.java). This is not a coincidence. In Java, all codes must reside inside a class and there is at most one public class which contain main() method.
  • By convention, the name of the main class(class which contain main method) should match the name of the file that holds the program.

Compiling the program :

  • After successfully setting up the environment, we can open ta terminal in both Windows/Unix and can go to the directory where the file – HelloWorld.java is present.
  • Now, to compile the HelloWorld program, execute the compiler – javac , specifying the name of the source file on the command line, as shown:
    javac HelloWorld.java 
    
  • The compiler creates a file called HelloWorld.class (in present working directory) that contains the bytecode version of the program. Now, to execute our program, JVM(Java Virtual Machine) needs to be called using java, specifying the name of the class file on the command line, as shown:
    java HelloWorld
    

    This will print “Hello World” to the terminal screen.

Python vs Java Comparison Summary

Here’s a quick comparison between the two languages we discussed.

Technology Python Java
Popularity Very popular Very popular
Syntax Easy to learn and use Complex includes a learning curve
Performance Slower than Java in various implementations Relatively very fast
Cross-Platform Yes Yes, thanks to the JVM
Backend Frameworks Django, Flask Spring, Blade
Machine Learning Libraries Tensorflow, Pytorch, Weka, Mallet, Deeplearning4j, MOA
Game Development Engines Cocos, Panda3d JMonkeyEngine

Java and Python are both capable and popular languages, so there won’t be a lack of resources once you choose one and embark on your journey. If you’re new to programming, it’d be better to stick with Python just because it’s really easy and uses English-like syntax, it’s used in many Computer Science introductory courses around the world. However, if your goal is to build enterprise-level applications coming from a C/ C++ world, then Java would probably feel pretty familiar to you. It all goes down on what you plan to build and where you feel like journeying with your new skill.

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