armstrong_number_checker.py

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#
# Program: Check If A Number Is An Armstrong Number
#
# Description: Program to check if a number is an armstrong number using Python.
# An Armstrong number is defined here, and also see informal definition below: 
# https://en.wikipedia.org/wiki/Narcissistic_number
#
# YouTube Lesson: https://www.youtube.com/watch?v=CKqrW31RRag 
#
# Author: Kevin Browne @ https://portfoliocourses.com
#
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# An Armstrong number is a number where the sum of each digit to the power of 
# the number of digits in the number is equal to the number itself.
#
# So for example 153 is an Armstrong number because...
#
# 153 = 1^3 + 5^3 + 3^3
# 153 = 1 + 125 + 27
# 153 = 153
#
# Where the number 153 has 3 digits, and so we take each digit 1,5,3, raise 
# them to the power of 3, and the sum of these numbers is equal to 153.
#
# To determine if a number is an Armstrong number or not we will need to 
# determine the number of digits in the number and 'extract' each digit in the
# number.  We can do this by dividing the number by 10, and continually 
# dividing the quotient of the previous division operation by 10 until the 
# quotient/number is equal to 0.  The number of division operations until the
# number is equal to 0 is the number of digits in the number, and the remainders
# of these division operations are the digits...
#
# 153 / 10 = 15 remainder 3
# 15 / 10  = 1 remainder 5
# 1 / 10   = 0 remainder 1
#
# In Python we can get the quotient of each division operation with the integer
# division operation // and the remainder with the modulus operator %...
#
# // - integer division, quotient
#  % - modulus, remainder


# Returns the number of digits in the number
def count_digits(number):

  # Stores running count of digits in the number
  digits = 0
  
  # So long as the number has not yet reached 0, take the number and divide it
  # by 10 and store the resulting quotient back into the number.  Increment 
  # digits each time by 1 to acknowledge there is another digit in the number.
  while number != 0:
    number = number // 10 
    digits += 1
  
  # Return the number of digits in the number
  return digits 


# Returns true if the number n is an Armstrong number and false otherwise
def is_armstrong(n):
  
  # Find the number of digits in the number using the above function and store
  # the resulting return value into the variable number_of_digits
  number_of_digits = count_digits(n)
  
  # Following the same process as in count_digits, we'll go through each digit
  # in the number n.  This will involve modifying the number.  We still need 
  # a copy of the 'original number' because we'll be comparing the original 
  # number to the sum of each digit of the number raised to the power of the 
  # number of digits in the number to determine if the number is an Armstrong
  # number or  not.  So we make a copy of the number n, called temp.
  temp = n 

  # Will store the running sum of each digit in the number raised to the power
  # of the number of digits in the number
  sum = 0
  
  # Extracts each digit in the number, raises it to the power of the number of 
  # digits in the number, and adds the resulting number to sum.  The number 
  # is continually divided by 10 until it is equal to 0 (at which point the 
  # loop stops) in order to go through each digit in the number
  while temp != 0:

    # Extract the digit using modulus which returns the remainder of dividing
    # the number by 10
    digit = temp % 10

    # Take the number and divide it by 10, so we can keep going through the 
    # number one digit at a time
    temp = temp // 10

    # Take the digit, raise it to the power of number of digits using the power
    # operator **, and add the result to sum
    sum += digit ** number_of_digits

  # Check if the resulting sum is equal to n, if it is, the number is an 
  # Armstrong number and the function returns true, otherwise it is not an 
  # Armstrong number and the function returns false
  return sum == n

# Check if the number 153 is an Armstrong number (it is!)
print(is_armstrong(153))