Numbers — The Full Picture

The idea!

You've covered a lot. int, float, arithmetic, the math module, two real projects.

This is your reference. Everything in one place.

Come back here whenever you need a reminder.

Number Types

age = 25       # int — whole number
height = 1.80  # float — decimal number

print(type(age))     # <class 'int'>
print(type(height))  # <class 'float'>

Python assigns the type automatically. No quotes — it's a number.

Arithmetic Operators

print(10 + 3)   # 13  — addition
print(10 - 3)   # 7   — subtraction
print(10 * 3)   # 30  — multiplication
print(10 / 3)   # 3.333... — division (always float)
print(10 // 3)  # 3   — floor division (int)
print(10 % 3)   # 1   — modulo (remainder)
print(10 ** 3)  # 1000 — exponentiation

int vs float

print(10 / 2)         # 5.0 — division always returns float
print(10 // 2)        # 5   — floor division returns int
print(int(3.9))       # 3   — truncates, does not round
print(float(5))       # 5.0
print(5 + 2.0)        # 7.0 — mixing returns float
print(0.1 + 0.2)      # 0.30000000000000004 — float precision

Conversion

print(int(3.9))    # 3   — truncates
print(float(5))    # 5.0
print(str(25))     # "25" — number to string
print(int("25"))   # 25  — string to number

Rounding

print(round(3.14159, 2))  # 3.14
print(round(3.5))          # 4
print(round(2.5))          # 2 — banker's rounding

The math module

import math

print(math.pi)          # 3.141592653589793
print(math.sqrt(16))    # 4.0
print(math.pow(2, 8))   # 256.0
print(math.floor(3.9))  # 3
print(math.ceil(3.1))   # 4

Input with numbers

# input() always returns string — convert before math
age = int(input("Enter your age: "))
height = float(input("Enter your height: "))
print(f"Age: {age} | Height: {height}")

Common Mistakes

• Division / always returns float — use // for int
• int() truncates — use round() for rounding
• Float precision is a known quirk — not a bug
• Input always returns string — convert before math
• Division by zero crashes — always
• Operator precedence applies — use parentheses when in doubt

What you should understand now

• int and float are different types — Python assigns them automatically
• Division always returns float
• The math module gives you sqrt, floor, ceil, pi, pow and more
• Always convert input() before doing math