script_4.py - Factorial Calculator

Code

#!/usr/bin/env python3
"""Factorial calculator"""

n = int(input("Enter a number: "))
factorial = 1

for i in range(1, n + 1):
    factorial *= i

print(f"{n}! = {factorial}")

Explanation

Line 4: n = int(input("Enter a number: ")) - n stores the integer to calculate factorial for

Line 5: factorial = 1 - Accumulator initialized to 1 (not 0!) - Must be 1 because we're multiplying (0 would make result always 0) - Integer type

Line 7: for i in range(1, n + 1): - Iterates from 1 to n (inclusive) - Loop variable i takes each value in sequence

Line 8: factorial *= i - *= is augmented assignment for multiplication - Equivalent to factorial = factorial * i - Multiplies accumulator by current loop value - Example for n=5: 1×1=1, then 1×2=2, then 2×3=6, then 6×4=24, then 24×5=120 - Builds up factorial through repeated multiplication

Line 10: print(f"{n}! = {factorial}") - ! is factorial symbol in mathematics - Shows final result after all iterations complete