Master Guide to Operators and Expression Evaluation in Python

Hello Everyone! Today we are going to explore Operators in Python. Operators are special symbols that perform computations, comparisons, and logical checks on data. Python provides a rich set of operators that make writing complex logic incredibly simple.

Let’s break them down category by category.

1. Arithmetic Operators

Arithmetic operators are used to perform mathematical calculations.

Operator Meaning Example (a = 5, b = 2) Output
+ Addition a + b 7
- Subtraction a - b 3
* Multiplication a * b 10
/ Division a / b 2.5 (Always returns a float!)
// Floor Division a // b 2 (Gives the integer part only)
% Modulus (Remainder) a % b 1 (Remainder of $5 \div 2$)
** Exponentiation (Power) a ** b 25 ($5^2$)

Special Python Tricks with Arithmetic Operators

  • String Concatenation (+): Joins text together: "Hello " + "World" $\rightarrow$ "Hello World".
  • String Replication (*): Repeats text multiple times: "-" * 10 $\rightarrow$ ----------.
  • Fractional Powers: You can find roots using fractions: 49 0.5 gives 7.0.

2. Operator Precedence (BODMAS vs. PEMDAS)

When evaluating mathematical expressions, Python follows strict priority rules similar to algebraic rules:

  1. Parentheses ()** (Highest Priority)
  2. Exponentiation **
  3. Multiplication *, Division /, Floor Division //, Modulus %** (Left-to-right)
  4. Addition +, Subtraction -** (Lowest Priority)
# Let's trace this calculation:
print(2 * 2 + 2 / 2) 
# Step 1: 2 * 2 = 4 and 2 / 2 = 1.0
# Step 2: 4 + 1.0 = 5.0

3. Comparison Operators

Comparison operators are used to compare two values. They always return a Boolean value: True or False.

Operator Meaning Example Result
> Greater Than 5 > 10 False
< Less Than 50 < 10 False
== Equal To 18 == 8 False
!= Not Equal To 18 != 18 False
> Greater Than or Equal To 188 >= 18 True
< Less Than or Equal To 1 <= 18 True

Note on String Comparisons: Python compares strings based on alphabetical order and ASCII values. Capital letters have smaller ASCII weights than lowercase letters (e.g., 'A' > 'a' evaluates to False).

4. Short-Hand / Assignment Operators

Assignment operators are used to assign values to variables. Short-hand operators combine an arithmetic operation with assignment to save space.

a = 60
a += 20  # Equivalent to: a = a + 20 -> Now a is 80
a -= 10  # Equivalent to: a = a - 10 -> Now a is 70
a **= 2  # Equivalent to: a = a ** 2 -> Now a is 4900

5. Logical Operators (and, or, not)

Logical operators allow you to combine multiple conditions. In Python, these operators evaluate using Short-Circuit Evaluation and can return actual values instead of just True/False.

The or Operator

  • Rule: If any value is true, it returns the first true value found from left to right. If all values are false, it returns the right-most false value.
print(False or False or 56 or True or 90) # Output: 56 (First Truthy value)
print("" or [] or 0 or None)             # Output: None (All are Falsy, picks last)

The and Operator

  • Rule: If any value is false, it immediately returns the first false value. If all values are true, it returns the right-most true value.
print(23 and 25 and "" and 9) # Output: "" (First Falsy value found)
print(23 and 25 and 100)      # Output: 100 (All are Truthy, picks last)

6. Membership and Identity Operators

Membership Operators (in, not in)

Used to check if a specific element or substring is present inside a sequence like a string or a list.

a = "I live in India."
print("India" in a)      # Output: True
print("x" not in "cat")  # Output: True

Identity Operators (is, is not)

Used to check if two variables point to the exact same memory location/object, not just whether their values match.

a = [1, 2]
b = [1, 2]
print(a == b)  # Output: True (Their values are identical)
print(a is b)  # Output: False (They are stored in different memory buckets)

Practical Laboratory Assignments

Here are practical script formulas built from our concepts to solve common foundation problems:

A. Finding 10% of a Number

a = float(input("Enter A Number: "))
print((a * 10) / 100)

B. Business Payroll Calculator

basic_pay = 1500
num_sold = int(input("Enter Num Of Cameras sold: "))

total_bonus = num_sold * 200
total_comm = (total_bonus + basic_pay) * 0.02
total_pay = basic_pay + total_bonus + total_comm

print(f"Total pay out: {total_pay}")

C. Calculating Geometric Area

# Area of Circle
radius = int(input("Enter radius: "))
print("Area of a circle is:", 3.14 * radius * radius)