This content originally appeared on DEV Community and was authored by Shahrouz Nikseresht
Welcome to Day 40 of the #80DaysOfChallenges journey! This intermediate challenge explores finding Armstrong numbers (also called narcissistic numbers) in a given range, where a number equals the sum of its own digits each raised to the power of the number of digits. It combines digit extraction via strings, exponentiation, loop-based checking, and a helper function for clean logic, making it a solid exercise in numeric manipulation and conditionals. If you're advancing from basic loops to algorithmic checks or enjoy math-inspired problems, this "Python Armstrong numbers" script demonstrates a function that's efficient for reasonable ranges and easy to extend for larger bounds or optimizations.
💡 Key Takeaways from Day 40: Armstrong Number Checker
This task features a core is_armstrong function that verifies a single number, used in a range loop to collect matches with input validation. It's a classic pattern: convert to string for digits, compute power sum, compare. We'll detail: helper with string digit access, range loop with collection, and input handling with guards.
1. Checker Function: String-Based Digit Power Sum
The is_armstrong function determines if n qualifies:
def is_armstrong(n: int) -> bool:
"""
Return True if n is an Armstrong number.
"""
s = str(n)
power = len(s)
total = 0
# Sum each digit raised to 'power'
for d in s:
total += int(d) ** power
return total == n
Converting to string gives easy digit access and len for power (e.g., 153 has 3 digits). Loop converts each char digit back to int, raises to power, sums. Compares to original n. For 153: 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153, True. Handles singles (1-9 are Armstrong) and zeros correctly.
2. Range Search: Input, Validation, Collection
Main script prompts and scans:
start = int(input("Start: "))
end = int(input("End: "))
# Validate range
if start < 0 or end < 0:
print("Range must contain non-negative integers only.")
raise SystemExit
if start > end:
print("Invalid range: start must be <= end.")
raise SystemExit
# Collect Armstrong numbers
armstrong_nums = []
for num in range(start, end + 1):
if is_armstrong(num):
armstrong_nums.append(num)
Validates non-negative and order, exits cleanly on issues. Loops inclusive end+1, appends matches. Efficient for typical ranges (up to ~10^6), as string ops scale with digits (~log n).
3. Output: List or None Found
Final print:
# Output result
if armstrong_nums:
print("Armstrong numbers in this range:")
print(*armstrong_nums)
else:
print("No Armstrong numbers found in this range.")
Uses * for space-separated list, clean for few results. Handles empty gracefully.
🎯 Summary and Reflections
This Armstrong finder blends math and code cleanly, using string digits for simplicity. It reinforced:
- Digit extraction: String over mod/division, readable and fast enough.
- Power reuse: Len once for exponent.
- Validation early: Guards prevent bad runs.
Known Armstrongs are rare (only 88 below 10^18), so outputs sparse. For fun, precompute list.
Advanced Alternatives: Math way: while n: digit = n%10; total += digit**power; n//=10. Or generator for infinite. Your math check? Share!
🚀 Next Steps and Resources
Day 40 mixed math with loops, ready for number theory. In #80DaysOfChallenges? Found big ones? Post!
- Source Code for Challenge #40: scripts/armstrong_numbers.py
- Main Repository: 80-days-of-challenges
- Daily Updates: Twitter/X (@Shahrouzlogs)
This content originally appeared on DEV Community and was authored by Shahrouz Nikseresht
Shahrouz Nikseresht | Sciencx (2025-11-20T05:00:06+00:00) Day 40: Python Armstrong Numbers Finder, Detect Narcissistic Numbers in a Range with Digit Power Sum. Retrieved from https://www.scien.cx/2025/11/20/day-40-python-armstrong-numbers-finder-detect-narcissistic-numbers-in-a-range-with-digit-power-sum/
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