Introduction to Python Programming

What Exactly is Python? A Closer Look

At its heart, Python is a high-level, interpreted, general-purpose programming language. But what do these terms really mean for you, especially coming from C?

• High-Level: This means Python abstracts away the complexities of computer hardware. You don't manage memory explicitly (like `malloc` in C); Python handles it for you. Your code is closer to human language, making it faster to write and easier to understand.
• Interpreted Language:

  Unlike C, which is a compiled language (where your entire source code is converted into machine code before execution), Python uses an interpreter. This means:

  • Code is executed line-by-line.
  • You get immediate feedback on errors, simplifying debugging.
  • The development cycle (write code, run, test) is much quicker.

  Interview Tip: A common question is to compare interpreted vs. compiled languages. Remember, interpreted languages generally offer faster development but might be slower at runtime than highly optimized compiled languages for pure computational tasks. However, Python's efficient underlying C implementations for many operations often bridge this gap.

• General-Purpose: Python isn't niche. It's incredibly versatile, used across almost every domain imaginable, from web servers to scientific simulations.

Python's most celebrated feature is its readability. It enforces clear, consistent indentation (unlike C's reliance on curly braces), which makes code look clean and is often referred to as "executable pseudocode." This adherence to clear structure is part of what makes a code "Pythonic."

The Zen of Python: Python even has its own guiding principles for writing good code, accessible by typing `import this` in your Python interpreter. It emphasizes beauty, simplicity, explicitness, and readability.

Setting Up Your Python Environment: The Foundation

A proper setup ensures a smooth learning experience. Let's get your workstation ready for Python development.

1. Installing Python: Your Gateway

The simplest and recommended way is to download the official installer from python.org/downloads/.

• Windows: Download the executable installer. During installation, CRITICALLY IMPORTANT: Check the box "Add Python.exe to PATH". This step simplifies running Python from any terminal window.
• macOS: Python 2 used to be pre-installed, but it's deprecated. Download the macOS installer from python.org.
• Linux: Python is often pre-installed, but it's good practice to install the latest version via your distribution's package manager (e.g., `sudo apt install python3` on Ubuntu) or from source.

After installation, open your terminal (Command Prompt/PowerShell on Windows, Terminal on macOS/Linux) and verify your installation:

$ python --version
Python 3.10.12  (or similar version number)
$ python3 --version
Python 3.10.12  (often necessary on Linux/macOS)

If you see a version number (like "Python 3.10.12"), great! Your PATH is set up correctly, and Python is ready.

2. Your Development Environment: Where the Magic Happens

While a basic text editor works, an Integrated Development Environment (IDE) or a feature-rich code editor will dramatically boost your productivity.

• VS Code (Visual Studio Code):

  A fantastic choice for beginners and professionals. It's free, lightweight, and extensible.

  • Download from code.visualstudio.com.
  • Once installed, go to the Extensions view (Ctrl+Shift+X or Cmd+Shift+X) and search for the "Python" extension by Microsoft. Install it. This provides intelligent code completion, linting, debugging, and more.
• PyCharm (Community Edition):

  A highly powerful, dedicated Python IDE. If you plan to delve deep into large-scale Python projects, PyCharm's comprehensive tools are invaluable. The Community Edition is free.

  • Download from jetbrains.com/pycharm/download.

For this UdaanPath course, any of these will work perfectly, but VS Code with the Python extension provides a great balance of features and ease of use.

1. The Python Interactive Interpreter (REPL)

Python comes with an interactive shell, often called a REPL (Read-Eval-Print Loop). This is fantastic for testing small snippets of code quickly without saving a file.

How to launch it:

Open your terminal and just type `python` (or `python3` on some systems) and press Enter.

$ python
Python 3.10.12 (main, ...)
[GCC ...] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 

The `>>>` is the Python prompt, indicating it's ready for your input. Let's try our first command:

>>> print("Hello, UdaanPath!")
Hello, UdaanPath!
>>> 2 + 3
5
>>> "Udaan" + "Path"
'UdaanPath'

To exit the REPL, type `exit()` and press Enter, or press `Ctrl+Z` (Windows) or `Ctrl+D` (macOS/Linux).

2. Running Python Scripts: Your First Program File

For anything beyond a quick test, you'll write your code in a file, typically ending with the `.py` extension. This is how real-world Python applications are built.

Code Snippet:

# This is a comment. Python ignores anything after a '#' on a line.
# Comments are for humans to understand the code!

# The 'print()' function displays output to the console.
print("Namaste and Welcome, UdaanPath learners!")

# You can print multiple things!
print("This is your first Python script. How exciting!")

# Let's do a simple calculation
result = 10 + 5
print("10 + 5 =", result)

# A bit of UdaanPath branding
platform_name = "UdaanPath"
print(f"You're learning on {platform_name}!")
                    

Explanation of the code:

• Lines starting with `#` are comments. They are ignored by Python but are vital for explaining your code.
• `print()`: This is a built-in Python function used to display information (text, numbers, results of calculations) on your screen or terminal.
• `result = 10 + 5`: This is a simple assignment. We perform an addition and store its result (15) into something called a `variable` named `result`. More on variables in the next chapter!
• `f"You're learning on {platform_name}!"`: This is an f-string (formatted string literal), a modern way to embed variables directly into strings. Very handy!

How to Run this Script:

Save the code above as `welcome_udaanpath.py` using your chosen editor (VS Code recommended). Open your terminal, navigate to the directory where you saved the file, and then execute it:

$ cd /path/to/your/python/files
$ python welcome_udaanpath.py
Namaste and Welcome, UdaanPath learners!
This is your first Python script. How exciting!
10 + 5 = 15
You're learning on UdaanPath!

If you see the output exactly as shown, congratulations! Your Python environment is fully functional, and you've successfully executed your first Python script.