Operators, Input and f-Strings in Python

Operators do calculations and comparisons. Together with input() and f-strings, they let you write your first useful programs.

1. Arithmetic operators

print(17 / 5, 17 // 5, 17 % 5, 2 ** 5)

3.4 3 2 32

% is very useful: n % 2 == 0 checks if n is even; n % 10 gives the last digit.

2. Comparison and logical operators

Comparisons give True or False: == (equal), != (not equal), >, <, >=, <=.

Logical operators combine them: and (both true), or (at least one), not (flip).

age = 20
has_id = True
print(age >= 18 and has_id)
print(age < 18 or not has_id)
print(10 == 10.0, "a" != "A")

True
False
True True

3. Assignment shortcuts

x += 5 means x = x + 5. Also -=, *=, /=, //=, %=.

score = 10
score += 5
score *= 2
print(score)

30

4. Precedence (which runs first)

From highest to lowest: ** → * / // % → + - → comparisons → not → and → or. Use brackets when in doubt.

print(2 + 3 * 4, (2 + 3) * 4, 2 ** 3 ** 2)

14 20 512

(** works right to left: 2 ** (3 ** 2) = 2⁹ = 512.)

5. Taking input

input() waits for the user to type something and always returns a string. Convert it for maths.

# Input: Asha
# Input: 20
name = input()
age = int(input())
print("Hello", name)
print("Next year you will be", age + 1)

Hello Asha
Next year you will be 21

(When you run it yourself, you type Asha and 20. You can also show a prompt: input("Enter your name: ").)

Reading two numbers on one line:

# Input: 12 30
a, b = map(int, input().split())
print(a + b)

42

input().split() splits the line at spaces; map(int, …) converts each part to an int.

6. f-strings: clean output

Put f before the quotes and write variables inside { }.

name = "Ravi"
marks = 87.456
print(f"{name} scored {marks:.2f} marks")
print(f"{'Item':<8}{'Price':>8}")
print(f"{'Pen':<8}{10:>8}")

Ravi scored 87.46 marks
Item       Price
Pen           10

• :.2f → 2 decimal places
• :<8 → left-align in 8 characters, :>8 → right-align

Common mistakes

• Forgetting that input() gives a string: input() + 1 is a TypeError.
• Using / when you need a whole number — use //.
• Using = (assignment) instead of == (comparison) in conditions.

Quick recap

• / gives a float; // floor division; % remainder; ** power.
• and, or, not combine conditions.
• input() returns a string — convert with int() / float().
• f-strings: f"{value:.2f}" for neat output.