Python Tutorials

First Python Program

3 min read

Now that you have successfully installed Python and set up your IDE, it is time to write your first Python program. In the programming world, it is a tradition to start by printing the message “Hello, World!” on the screen.

Python provides two different ways to run a program:

  1. Interactive Mode (Running code line-by-line in the terminal)
  2. Script Mode (Writing code in a file and executing it)

Let us explore both methods.

Method 1: Using Interactive Mode

Interactive mode is useful for testing short snippets of code quickly. It executes one line of code at a time and immediately shows the output.

Steps to Run Code in Interactive Mode:

  1. Open your Command Prompt (Windows) or Terminal (macOS/Linux).
  2. Type python and press Enter. You will see the Python version and a prompt looking like >>>. This means the Python shell is active.
  3. Type the following code next to the >>> prompt and press Enter:
print("Hello, World!")
Code language: PHP (php)

Output:

Hello, World!

Note: To exit the interactive mode, type exit() and press Enter.

Method 2: Using Script Mode (Recommended)

While interactive mode is good for quick testing, you cannot save your code there. For actual software development, we write our code in a file and save it with a .py extension. This is called Script Mode.

Steps to Run Code in Script Mode:

  1. Open your code editor (like VS Code or PyCharm) or a basic text editor like Notepad.
  2. Create a new file and name it hello.py. The .py extension is mandatory for Python files.
  3. Write the following code inside the file:
# This is our first Python program
print("Hello, World!")
Code language: PHP (php)
  1. Save the file.
  2. Open your terminal or command prompt, navigate to the folder where you saved hello.py, and run the following command:
python hello.py
Code language: CSS (css)

Output:

Hello, World!

Understanding the Code

Let us break down the simple one-line code we just wrote to understand how Python works:

  • # This is our first Python program: The # symbol is used to write comments. The Python interpreter ignores comments during execution. They are used to make the code easier to understand for humans.
  • print(): This is a built-in Python function. Its job is to display whatever is placed inside the parentheses () onto the screen.
  • "Hello, World!": The text enclosed in double quotes (or single quotes) is called a String. A string is simply a sequence of characters.

Common Mistakes Beginners Make

When writing your first program, you might encounter some errors. Here are the most common mistakes and how to fix them:

1. Missing Parentheses

In Python 3, the print statement requires parentheses. Wrong: print "Hello, World!" Error: SyntaxError: Missing parentheses in call to 'print'. Correction: Always use print("...").

2. Missing Quotes

If you are printing text, it must be inside quotes. Wrong: print(Hello, World!) Error: SyntaxError: invalid syntax Correction: Ensure text is enclosed in " " or ' '.

3. Case Sensitivity

Python is a case-sensitive language. Uppercase and lowercase letters are treated differently. Wrong: Print("Hello, World!") (Capital ‘P’) Error: NameError: name 'Print' is not defined Correction: Always use lowercase print().

4. Unnecessary Spaces (Indentation Error)

In Python, spaces at the beginning of a line have a special meaning. Wrong: “`python print(“Hello, World!”) # Notice the space at the start

**Error:** `IndentationError: unexpected indent`
**Correction:** Make sure the `print` statement starts exactly at the beginning of the line without any leading spaces.
Code language: JavaScript (javascript)

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