Python Basics

Python Basics: Variables, Datatypes, Keywords, and Literals

This guide provides a beginner-friendly introduction to variables, datatypes, keywords, and literals in Python, with examples and explanations.
1. Variables
Definition

Variables are containers for storing data values. In Python, you don’t need to declare a variable type explicitly. The type is inferred when you assign a value.

Syntax:

variable_name = value

Rules

Must start with a letter or an underscore _.
Cannot start with a number.
Can contain letters, numbers, and underscores.
Case-sensitive (name and Name are different).

Example:

# Assigning values to variables
x = 10           # Integer
name = "Alice"   # String
_pi = 3.14       # Float
is_valid = True  # Boolean

# Printing variables
print(x, name, _pi, is_valid)

10 Alice 3.14 True

2. Datatypes
Definition

Datatypes define the type of data a variable can hold.

Common Datatypes

Datatype	Description	Example
int	Integer numbers	x = 5
float	Decimal numbers	y = 3.14
str	Text or string data	name = "Python"
bool	True/False values	is_valid = True
list	Ordered collection of items	nums = [1, 2, 3]
tuple	Immutable ordered collection	coords = (10, 20)
dict	Key-value pairs	person = {"name": "Alice", "age": 25}
set	Unordered collection of unique items	unique_nums = {1, 2, 3}

Examples

#### Integer
age = 25
print(type(age))  # Output: <class 'int'>

#### Float
price = 19.99
print(type(price))  # Output: <class 'float'>

#### String
greeting = "Hello, World!"
print(type(greeting))  # Output: <class 'str'>

#### List
colors = ["red", "green", "blue"]
print(type(colors))  # Output: <class 'list'>

#### Dictionary
person = {"name": "Alice", "age": 30}
print(type(person))  # Output: <class 'dict'>

3. Keywords

Definition
Keywords are reserved words in Python. They have a special meaning and cannot be used as variable names.

Examples of Keywords

and, or, not, if, else, while, for, import, def, class, True, False, None, return, etc. Usage

#### Using keywords
if True:
    print("This is a keyword example.")

Check All Keywords

import keyword
print(keyword.kwlist)

4. Literals
Definition

Literals are fixed values assigned to variables or used directly in expressions.

Types of Literals

Literal Type	Description	Example
Numeric	Integer, Float, Complex	10, 3.14, 2 + 3j
String	Text data	"Hello", 'Python'
Boolean	Logical True/False Values	True, False
Special	Represents absence of value	None

Examples

#### Numeric Literals
int_literal = 100
float_literal = 20.5
complex_literal = 3 + 4j

#### String Literals
single_quote = 'Hello'
double_quote = "World"

#### Boolean Literals
is_active = True

#### Special Literal
empty_value = None

print(int_literal, float_literal, complex_literal, single_quote, double_quote, is_active, empty_value)

Output:

100 20.5 (3+4j) Hello World True None

5. Python is Dynamically Typed

Python doesn’t require you to specify the type of a variable. The type is determined automatically based on the value assigned. Example

x = 10         # x is an integer
x = "Python"   # Now x is a string
print(x)       # Output: Python

6. Example Program

# Define variables
name = "Alice"
age = 30
is_student = False
grades = [85, 90, 92]

# Display information
print(f"Name: {name}\n")
print(f"Age: {age}\n")
print(f"Is Student: {is_student}\n")
print(f"Grades: {grades}")

Output:

Name: Alice

Age: 30

Is Student: False

Grades: [85, 90, 92]

Quick Tips

Use meaningful variable names (e.g., price, age, username).
Use type() to check the datatype of a variable.
Use comments (#) to explain your code.

This guide provides the foundation for understanding Python's core concepts. Keep practicing, and soon you'll master them! 😊