Class06,07 Operators, Expressions

In Python, operators are special symbols that perform operations on variables and values. They are categorized based on their functionality: ⚙️

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1. Arithmetic Operators ➕➖✖️➗

Used for mathematical operations:

• + (Addition)
• - (Subtraction)
• * (Multiplication)
• / (Division → float)
• // (Floor Division → integer)
• % (Modulus → remainder)
• ** (Exponentiation)

Python

print(5 + 3)    # 8
print(10 // 3)  # 3 (integer division)
print(2 ** 4)   # 16 (2^4)

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2. Assignment Operators ➡️

Assign values to variables (often combined with arithmetic):

• = (Assign)
• += (Add and assign)
• -= (Subtract and assign)
• *= (Multiply and assign)
• /= (Divide and assign)
• //= (Floor divide and assign)
• %= (Modulus and assign)
• **= (Exponentiate and assign)

Python

x = 5
x += 2  # Equivalent to x = x + 2 → 7
print(x) # Output: 7

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3. Comparison Operators ⚖️

Compare values → return True or False:

• == (Equal)
• != (Not equal)
• > (Greater than)
• < (Less than)
• >= (Greater than or equal to)
• <= (Less than or equal to)

Python

print(5 == 5)  # True
print(10 > 12) # False

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4. Logical Operators 💡

Combine conditional statements:

• and → True if both operands are true
• or → True if at least one operand is true
• not → Inverts the result

Python

print((5 > 3) and (10 < 20))  # True
print(not (5 == 5))            # False

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5. Identity Operators 🆔

Check if objects are the same in memory:

• is → True if both variables point to the same object
• is not → True if they are different objects

Python

a = [1, 2]
b = a
c = [1, 2]
print(a is b)  # True (same object)
print(a is c)  # False (different objects, even if same content)

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6. Membership Operators 📍

Test if a value exists in a sequence (list, tuple, string, etc.):

• in → True if value is found
• not in → True if value is missing

Python

fruits = ["apple", "banana"]
print("banana" in fruits)     # True
print("grape" not in fruits)  # True

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7. Bitwise Operators 🧮

Operate on binary representations:

• & (AND)
• | (OR)
• ^ (XOR)
• ~ (NOT)
• << (Left shift)
• >> (Right shift)

Python

print(5 & 3)  # 1 (binary: 101 & 011 = 001)
print(5 >> 1) # 2 (binary 101 shifted right → 10)

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Operator Precedence 📏

Order of evaluation (highest to lowest):

1. Parentheses () 괄호
2. Exponentiation ** ⬆️
3. Bitwise shifts <<, >> ⬅️➡️
4. Multiplication/Division *, /, //, % ✖️➗
5. Addition/Subtraction +, - ➕➖
6. Comparison ==, !=, >, etc. ⚖️
7. Logical NOT not ✖️
8. Logical AND and 🤝
9. Logical OR or ➕

Example:

Python

result = 10 + 3 * 2  # 16 (3*2=6 → 10+6)
print(result) # Output: 16

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Key Notes: 📌

• Type Compatibility: Operators may behave differently based on data types (e.g., + concatenates strings but adds numbers). 📊
• Chaining Comparisons: Python allows a < b <= c. 🔗
• Short-Circuiting: Logical operators (and/or) stop evaluating once the result is determined. ⚡

Expressions in Python

An expression is a combination of values, variables, operators, and function calls that Python evaluates to produce a single value. Expressions can be as simple as a single variable or as complex as a multi-operation calculation.

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Key Characteristics of Expressions:

1. Always evaluate to a value (e.g., 5 + 3 → 8)
2. Can contain operators, literals, variables, and function calls
3. Can be part of larger statements (e.g., inside if conditions, assignments)

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Arithmetic Expression Examples

Example	Evaluation	Explanation
5 + 3 * 2	11	Multiplication before addition
(5 + 3) * 2	16	Parentheses change order
10 / 3	3.333...	Regular division (float result)
10 // 3	3	Floor division (integer result)
10 % 3	1	Modulus (remainder)
2 ** 4	16	Exponentiation (2⁴)
-5 + 8	3	Unary negative + addition
3.5 * (2 + 1)	10.5	Mixed float/integer operations
(2 + 3j) * (1 - 1j)	(5+1j)	Complex number arithmetic

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Expression Types with Examples

1. Simple Arithmetic

python

x = 5
y = 3
result = x * y - 2  # Evaluates to 13 (5*3=15 → 15-2)

2. With Functions

python

import math
hypotenuse = math.sqrt(3**2 + 4**2)  # √(9+16) = 5.0

1. Area of a Triangle

Area = 0.5 × base × height

2. Area of a Trapezium

Area = 0.5 × (a + b) × height
(where a and b are the lengths of the parallel sides)

3. Area of a Circle

Area = π × radius²
(π ≈ 3.14159)

4. Kilometers to Miles

Miles = Kilometers × 0.621371

5. Displacement (Physics)

s = u×t + ½×a×t²
(where u = initial velocity, t = time, a = acceleration)

6. Surface Area of a Cuboid

Surface Area = 2 × (lw + wh + hl)
(where l = length, w = width, h = height)

More Area/Volume/Surface Area Calculations:

• Area of a Rectangle/Square: Simple and fundamental.
• Area of a Parallelogram: Similar to a rectangle but with an angle consideration.
• Area of a Rhombus: Can be calculated using diagonals.
• Volume of a Cube: Straightforward.
• Volume of a Cuboid: Extension of a cube.
• Volume of a Cylinder: Involves pi and radius/height.
• Volume of a Cone: Related to a cylinder but with a factor of 1/3.
• Volume of a Sphere: Involves pi and radius cubed.
• Surface Area of a Cylinder: Two circles and a rectangle.
• Surface Area of a Cone: Base circle and a lateral surface.
• Surface Area of a Sphere: Simple formula involving pi and radius squared.
• Perimeter of a Rectangle/Square: Basic perimeter calculation.
• Circumference of a Circle: Directly related to the area of a circle.
• Area of a Sector of a Circle: A fraction of the circle’s area.

Conversions:

• Miles to Kilometers: Reverse of your existing program.
• Celsius to Fahrenheit: Common temperature conversion.
• Fahrenheit to Celsius: Reverse of the above.
• Pounds to Kilograms: Weight conversion.
• Kilograms to Pounds: Reverse of the above.
• Liters to Gallons: Volume conversion.
• Gallons to Liters: Reverse of the above.
• Meters to Feet: Length conversion.
• Feet to Meters: Reverse of the above.
• Hours to Minutes/Seconds: Time unit conversions.

Physics/Math Formulas:

• Calculate Velocity: Velocity=Displacement/Time
• Calculate Acceleration: Acceleration=ChangeinVelocity/Time
• Calculate Force: Force=Mass×Acceleration (Newton’s Second Law)
• Calculate Work Done: Work=Force×Distance
• Simple Interest Calculation: SimpleInterest=(Principal×Rate×Time)/100
• Compound Interest Calculation: More complex, involves exponents.
• Quadratic Equation Solver: Finds roots of a quadratic equation.
• Pythagorean Theorem: a2+b2=c2 (calculating hypotenuse or a side of a right triangle).
• Body Mass Index (BMI) Calculator: Based on height and weight.
• Ohm’s Law: Voltage=Current×Resistance (or variations to find current/resistance).