Numbers and Variables in Python: Definitions

1. Variable Definition in Python

Python does not require manual type declaration for variables. The type is automatically inferred from the assigned value.

x = 5           # Integer variable
name = "Python" # String variable
pi = 3.14       # Floating-point variable

• Dynamic: Types are inferred automatically
• Mutable: Variable values can be reassigned during execution

2. Dynamic Typing

Python supports dynamic typing—variable types change based on the value assigned:

x = 5
print(type(x))   # Output: 

x = "Hello"
print(type(x))   # Output: 

• Flexible for rapid development
• No need for manual type conversion

3. Numeric Types in Python

Type	Example	Description
int	5	Whole number
float	3.14	Decimal number
complex	2 + 3j	Complex number (real + imaginary)

Mathematical operations can be performed directly:

a = 10
b = 3.5
print(a + b)    # Output: 13.5

4. Strings in Python

Strings are sequences of characters and can be defined using single or double quotes:

text = "Hello, Python!"

• Indexable and sliceable
• Useful for text processing and transformation

Common string operations:

message = "Python Programming"
print(len(message))                  # Count characters
print(message.upper())              # Convert to uppercase
print(message.lower())              # Convert to lowercase
print(message.replace("Python", "Java"))  # Replace word

5. Indexing and Slicing

Strings use zero-based indexing:

word = "Python"
print(word[0])     # Output: P
print(word[-1])    # Output: n (last character)

Slicing extracts specific portions of a string:

message = "Programming"
print(message[0:5])   # Output: Progr
print(message[:7])    # Output: Program
print(message[3:])    # Output: gramming