Variables & Data Types

Understanding variables, data types, and type conversion in Python.

Variables

Variables store data values.
No need to declare type - Python infers it automatically.
Variable names must start with letter or underscore.
Case-sensitive: 'age' and 'Age' are different variables.

# Creating variables
name = "Alice"
age = 25
height = 5.6
is_student = True

print(name, age, height, is_student)

Data Types

int: Whole numbers (1, 42, -10)
float: Decimal numbers (3.14, -0.5)
str: Text in quotes ('hello', "world")
bool: True or False
Use type() to check variable type.

# Different data types
x = 10           # int
y = 3.14         # float
name = "Python"  # str
active = True    # bool

print(type(x))    # <class 'int'>
print(type(name)) # <class 'str'>

Type Conversion

Convert between types using int(), float(), str(), bool().
Useful when reading user input or processing data.
Be careful - some conversions may fail or lose data.

# Type conversion
x = "123"
y = int(x)        # Convert string to int
print(y + 10)     # 133

a = 5
b = str(a)        # Convert int to string
print(b + "0")    # "50"

c = float("3.14") # Convert string to float
print(c * 2)      # 6.28

Multiple Assignment

Assign multiple variables in one line.
Swap variables without temporary variable.
Unpack values from lists or tuples.

# Multiple assignment
x, y, z = 1, 2, 3
print(x, y, z)  # 1 2 3

# Swap variables
a, b = 10, 20
a, b = b, a
print(a, b)     # 20 10

# Same value to multiple variables
x = y = z = 0