Python Basics — Day 2(Variables and Data Types)

01. What is a Variable?

• A variable is like a label that stores data.

• Use the = operator to assign a value.

x = 10          # Integer (int)
y = 3.14        # Floating-point number (float)
name = "Sabin"  # String (str)
is_ok = True    # Boolean (bool)

02. Basic Data Types (Primitive Data Types)

🔹 Integer (int)

• Whole numbers without a decimal point

age = 25
print(age, type(age))  # 25 <class 'int'>

- Float (float)

• Numbers with decimals

pi = 3.14159
print(pi, type(pi))  # 3.14159 <class 'float'>

- String (str)

• A sequence of characters (use double " " or single ' ' quotes)

greeting = "Hello"
print(greeting, type(greeting))  # Hello <class 'str'>

- Boolean (bool)

• Represents True or False

is_student = True
print(is_student, type(is_student))  # True <class 'bool'>

03. Variable Naming Rules

✅ Can contain letters, numbers, and underscores (_)
✅ Cannot start with a number
✅ Case-sensitive (Name ≠ name)
✅ Use descriptive names (recommended)

a = 10            # ❌ Not meaningful
student_age = 20  # ✅ Clear and descriptive

04. Type Casting

Convert between different data types.

# int → float
x = 10
print(float(x))  # 10.0

# float → int
y = 3.99
print(int(y))  # 3# str → int
num_str = "100"
print(int(num_str) + 1)  # 101# int → str
age = 25
print("Age: " + str(age))  # Age: 25

05. Practice Examples

📝 Example 1: Print Variables

name = "Ian"
age = 20
height = 189
is_student = False

print("Name:", name)
print("Age:", age)
print("Height:", height)
print("Is student?", is_student)

📝 Example 2: Type Casting

a = "5"
b = 10
# Convert the string "5" into an int before adding
print(int(a) + b)  # 15