Introduction to Python Variables, Types, and Basic Operations

Some Computer Basics

Before learning to program, it is useful to know that a computer consists of five major components: the arithmetic unit, the control unit, memory, input devices, and output devices. The arithmetic and control units together form the Central Processing Unit (CPU), which executes operations and controls instructions. Memory is divided into internal (RAM) and external storage. Input devices (keyboard, mouse, microphone, camera) and output devices (monitor, printer, speaker) are collectively called I/O devices. Modern computers follow the Von Neumann architecture, separating memory from the CPU and representing data in binary.

Binary is a base‑2 counting system where each digit represents a power of two. While programmers do not need to master binary, it is important to understand that all data inside a computer is stored in binary form.

Variables and Types

In programming, a variable is a container that holds data in memory; its value can be read and modified. Python provides several built‑in data types, including integers, floating‑point numbers, strings, and booleans. The most common types are introduced below.

Integer ( int ): Python integers have unlimited precision and can be written in binary ( 0b100 → 4), octal ( 0o100 → 64), decimal ( 100 ), or hexadecimal ( 0x100 → 256).

print(0b100)   # 4

print(0o100)   # 64

print(100)     # 100

print(0x100)   # 256

Floating‑point ( float ): Represents real numbers and supports scientific notation.

print(123.456)      # 123.456

print(1.23456e2)    # 123.456

String ( str ): Text enclosed in single or double quotes. print('hello') Boolean ( bool ): Two possible values, True and False .

print(True)

Variable Naming

Variable names must follow these rules and conventions:

Rule 1: Consist of letters, digits, and underscores; cannot start with a digit. Although Unicode letters are allowed, it is recommended to use only English letters.

Rule 2: Python is case‑sensitive, so A and a are different variables.

Rule 3: Do not use Python keywords or built‑in names (e.g., if, for, print, int).

Convention 1: Use lowercase letters with underscores for multi‑word names (e.g., my_variable).

Convention 2: Prefix a single underscore for protected variables.

Convention 3: Prefix double underscores for private variables.

Using Variables

Example of arithmetic operations with variables:

a = 45        # define variable a

b = 12        # define variable b

print(a, b)   # 45 12

print(a + b)  # 57

print(a - b)  # 33

print(a * b)  # 540

print(a / b)  # 3.75

Type Inspection and Conversion

The built‑in type() function reveals a variable's type. Conversion functions such as int(), float(), str(), chr(), and ord() change a value from one type to another.

a = 100

b = 123.45

c = 'hello, world'

d = True

print(type(a))  # <class 'int'>

print(type(b))  # <class 'float'>

print(type(c))  # <class 'str'>

print(type(d))  # <class 'bool'>

Examples of type conversion:

print(float(a))          # 100.0

print(int(b))            # 123

print(int('123'))        # 123

print(int('123', base=16))  # 291

print(int('100', base=2))   # 4

print(float('123.45'))   # 123.45

print(bool('hello'))      # True

print(int(True))         # 1

print(chr(100))          # 'd'

print(ord('d'))          # 100

Summary

In Python programs, variables store data and can be of different types such as int, float, str, and bool. Built‑in functions allow you to inspect and convert these types, and variables can participate in arithmetic operations, laying the foundation for solving more complex problems in subsequent lessons.