IDLE is a simple editor for Python that comes bundled with Python. In this tutorial, we will walk through the steps to create a "Hello, World" program using IDLE.

Step 1: Launching IDLE

To begin, let's open IDLE on our system. The process may vary depending on your operating system:

• For Windows Users:

  • On older versions of Windows, navigate to the "All Programs" section in the Start menu, find the Python folder, and click on "IDLE" to launch it.
  • If you're using Windows 8 or newer, you can search for "IDLE" directly from the Start menu or Start screen.

• For macOS Users:

  • Open a Finder window, go to the "Applications" folder, locate the Python folder, and double-click on "IDLE" to open it.

• For Linux Users:

  • Launch a terminal and type $ idle or $ idle3, then press Enter. This will start IDLE.

Step 2: Creating a New Python File

Once IDLE is open, we need to create a new Python file to write our "Hello, World" program:

• Click on File in the IDLE menu, then select New File from the dropdown menu.
• A new blank editor window will appear.

Step 3: Writing the "Hello, World" Program

Now, we can write our first Python program that will print the famous phrase "Hello, World":

print("Hello, World")

Step 4: Running the Program

After writing the program, it's time to execute it and see the output. Follow these steps:

• Click on Run in the IDLE menu, then choose Run Module or press F5.
• A new window, called the "Python Shell," will open, displaying the output:

Hello, World

Congratulations! You have successfully created and executed your first Python program using IDLE. You can modify the code and experiment with different outputs as you continue your Python learning journey.

Launching an Interactive Python Shell

In addition to running Python programs, IDLE also allows you to launch an interactive Python shell, where you can execute Python statements and see the results immediately. Here's how you can launch the interactive Python shell for both Python 2 and Python 3:

Launching Python 2 Shell:

• In IDLE, click on File in the menu, then select New Window or press Ctrl+N to open a new window.
• In the new window, you will see the interactive Python shell prompt represented by Python 2.7.12 (default, Jun 28 2016, 08:46:01) [GCC 6.1.1 20160602] on linux Type "help", "copyright", "credits" or "license" for more information.

Python 2.7.12 (default, Jun 28 2016, 08:46:01) 
[GCC 6.1.1 20160602] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> "hello,world"
'hello,world'
>>> 

• You can now enter Python statements and see the results interactively.

Launching Python 3 Shell:

• In IDLE, click on File in the menu, then select New Window or press Ctrl+N to open a new window.
• In the new window, click on Options in the menu, then select Configure IDLE.
• In the IDLE preferences window, go to the General tab.
• Under the Default Interpreter section, choose Python 3.x from the dropdown menu.
• Click on OK to save the changes and close the preferences window.
• Now, in the new window, you will see the interactive Python shell prompt represented by Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24) [Clang 6.0 (clang-600.0.57)] on darwin Type "help", "copyright", "credits" or "license" for more information.

Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24) 
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> "hello,world"
'hello,world'
>>> 

• You can now enter Python statements and see the results interactively.
• Launching the interactive Python shell provides a convenient way to experiment and test small snippets of code without the need for a complete Python program.

Useful Python Shell Commands:

The Python shell in IDLE provides several useful commands that can enhance your coding experience. Here are a few of them:

• Help: To get information about any Python function or module, you can use the help() command. For example:

  help(print)

• Clear: To clear the contents of the Python shell, you can use the clear() command. For example:

  clear()

• Exit: To exit the Python shell, you can use the exit() command. For example:

  exit()

These are just a few examples of the commands available in the Python shell. You can explore more commands and their functionalities as you progress in your Python journey.

To run Python 2 and Python 3 files through the command line on different operating systems, follow the instructions provided below:

Running Python 2 Files:

Windows:

• Open the Command Prompt.
• Navigate to the directory where your Python 2 file is located using the cd command.
• Run the Python 2 file using the command: python filename.py

macOS and Linux:

• Open the Terminal.
• Navigate to the directory where your Python 2 file is located using the cd command.
• Run the Python 2 file using the command: python filename.py

Running Python 3 Files:

Windows:

• Open the Command Prompt: You can open the Command Prompt on Windows by searching for "Command Prompt" in the Start menu or by pressing "Windows key + R" to open the Run dialog, then typing "cmd" and pressing Enter.

• Navigate to the directory: You can use the cd command to navigate to the directory where your Python 3 file is located. For example, if your Python file is located in "C:\Users\YourUsername\Documents\PythonFiles," you would use the following command:

  cd C:\Users\YourUsername\Documents\PythonFiles

  Replace "YourUsername" with your actual Windows username.

• Run the Python 3 file: The correct command to run a Python 3 file on Windows is simply "python" (not "python3") followed by the filename.

• python filename.py

  Replace "filename.py" with the actual name of your Python 3 file.

• So, the correct sequence of commands should be:

  cd C:\Users\YourUsername\Documents\PythonFiles
  python filename.py

  Please note that if you have installed Python via the Microsoft Store, you might need to use "python3" instead of "python" to run Python 3 files. However, for most installations of Python on Windows, using just "python" should work fine.

macOS and Linux:

• Open the Terminal.
• Navigate to the directory where your Python 3 file is located using the cd command.
• Run the Python 3 file using the command: python3 filename.py

Make sure to replace filename.py with the actual name of your Python file.

By specifying python or python3 before the filename, you explicitly choose the Python version to execute the file with.

Note: The commands mentioned above assume that you have both Python 2 and Python 3 installed on your system and that the python command is associated with Python 2, while python3 is associated with Python 3.

If you encounter any issues or if the commands don't work as expected, ensure that you have the correct Python versions installed and that the PATH environment variable is set up correctly.

Remember, on some systems, the python command may refer to Python 2 by default, while python3 is specifically associated with Python 3.

You can also specify the full path to the Python interpreter executable to run a file with a specific Python version.

Executing Python Commands from the Command Line

In Python, it's possible to run a single-line command directly from the command line using the python -c option. This provides a convenient way to quickly test or execute small snippets of Python code without the need for writing a separate Python file.

Command Syntax

The general syntax for running a Python command from the command line is as follows:

python -c 'command'

• python: This command is used to invoke the Python interpreter.
• -c: It is a command-line option for the Python interpreter that allows you to specify a command to be executed.
• 'command': The actual Python command to be executed, provided as a string.

Example Usage

Let's consider a simple example. Suppose we want to print the message "Hello, World" from the command line using Python. We can achieve this using the following command:

python -c 'print("Hello, World")'

When you run this command, the Python interpreter is invoked, and it executes the specified command. The output will be the "Hello, World" message printed to the console.

Benefits and Considerations

The python -c option is particularly useful for running concise, one-liner Python commands without the need to create a separate Python file. It provides a quick way to experiment with small code snippets or perform immediate tasks from the command line.

However, it's important to note that this method is more suitable for simple commands. For longer or more complex scripts, it is generally recommended to write the code in a separate Python file and execute it using the python filename.py command instead. This approach offers better readability, maintainability, and flexibility.

Remember to enclose the command in quotes (single or double) to ensure that the entire command is treated as a single argument by the command-line interpreter.

For more information on IDLE, you can refer to the official Python documentation.

If you haven't installed Python and IDLE yet, you can download the latest version from the official Python website.

Here are a few online Python shells where you can write and execute Python code directly in your web browser:

1. repl.it: It provides a simple and interactive online Python shell. You can write, run, and share Python code easily.

2. PythonAnywhere: It offers an online Python shell and development environment. You can execute Python code and also work on larger projects using their web-based IDE.

3. Trinket: It provides an online Python coding environment with an interactive shell. You can write and run Python code in real-time, as well as create and share Python programs.

4. Glot.io: It offers an online code editor and compiler for various programming languages, including Python. You can write and execute Python code directly in your browser.

Please note that while these online Python shells are convenient for quick testing and experimentation, they may have certain limitations compared to running Python locally on your machine.

Happy coding and enjoy exploring the world of Python!