Getting Started with Python

Python was created by Guido van Rossum and first released in 1991. It is a high-level, interpreted, general-purpose programming language. Python's design philosophy emphasizes code readability through its notable use of significant whitespace (indentation). It is wildly popular in fields ranging from Web Development to Artificial Intelligence and Data Science.

3.1 Features of Python

Python has several key characteristics that make it an excellent choice for both beginners and industry professionals:

• 1Easy to Learn and Read: Python's syntax is very close to plain English. It removes clutter like curly braces and semicolons.
• 2Interpreted Language: Python code is executed line-by-line by an interpreter, which makes debugging easier, though it can run slightly slower than compiled languages like C++.
• 3Platform Independent (Cross-Platform): Python code written on a Windows machine will run perfectly on a Mac or Linux machine without modification.
• 4Free and Open Source: Python is free to download, use, and distribute.
• 5Massive Standard Library: Python comes 'batteries included' with a huge library of pre-written code for tasks like networking, file I/O, and math.

3.2 Execution Modes

You can interact with Python in two primary ways: Interactive Mode and Script Mode.

• 1Interactive Mode: Using the Python shell (indicated by the `>>>` prompt). You type a single command, press Enter, and see the result immediately. It is excellent for quick testing and calculations, but code is not saved.
• 2Script Mode: You write multiple lines of code in a text file (with a `.py` extension) using an IDE like IDLE or VS Code. The entire file is then executed at once. This is how actual programs are written because the code is permanently saved.

3.3 Python Tokens

In a Python program, the smallest individual unit of code is called a Token. The Python interpreter breaks your code down into tokens before executing it. There are five main categories of tokens.

• 1Keywords: Reserved words that have special meaning to the interpreter. You cannot use them as variable names. Examples: `if`, `for`, `while`, `def`, `True`.
• 2Identifiers: Names created by the programmer to label variables, functions, and classes. (e.g., `age`, `calculate_sum`).
• 3Literals: Raw, fixed data values directly written into the code. Examples: `42` (Integer literal), `"Hello"` (String literal), `3.14` (Float literal).
• 4Operators: Symbols that trigger specific mathematical or logical computations. Examples: `+`, `-`, `=`, `==`, `and`.
• 5Punctuators (Delimiters): Symbols used to organize code structures. Examples: `( )`, `[ ]`, `:`, `,`.

3.4 Rules for Naming Identifiers

When creating a name for a variable or function (an identifier), you MUST follow strict Python rules. If you break these rules, Python will throw a SyntaxError.

• 1Must start with a letter (A-Z, a-z) or an underscore (_).
• 2CANNOT start with a number (e.g., `1st_place` is invalid).
• 3Can contain letters, numbers, and underscores, but NO other special characters (no spaces, no @, no $).
• 4Cannot be a reserved Python keyword (e.g., you cannot name a variable `if` or `for`).
• 5Python is case-sensitive! `Age`, `age`, and `AGE` are considered three entirely different variables.