Python - Compute the factorial of N with recursion (among others)

# Calculating the factorial of a number 
# is a good way to practice recursion. Below 
# are examples of both recursive and iterative 
# approaches to calculating a factorial. Of course 
# python has its own builtin math module that 
# can also take care of factorials. 
 
import math
 
# A recursive function to calculate the 
# factorial of N 
def recursiveFactorial(n):
    if n == 1:
        return n
    return n * recursiveFactorial(n - 1)
 
# Iterative calculation of the factorial 
# of N 
def iterativeFactorial(n):
    result = 1
    while n > 1:
        result *= n
        n = n-1
    return result
 
# Builtin python math.factorial of N 
def pythonLib(n):
    return math.factorial(n)
 
print("Iterative factorial of 5: ", iterativeFactorial(5))
print("Recursive factorial of 5: ", recursiveFactorial(5))
print("math.factorial of 5: ", pythonLib(5))
 
print("Iterative factorial of 10: ", iterativeFactorial(10))
print("Recursive factorial of 10: ", recursiveFactorial(10))
print("math.factorial of 10: ", pythonLib(10))
 
print("Iterative factorial of 15: ", iterativeFactorial(15))
print("Recursive factorial of 15: ", recursiveFactorial(15))
print("math.factorial of 15: ", pythonLib(15))
 
 
# my results: 
# Iterative factorial of 5:  120 
# Recursive factorial of 5:  120 
# math.factorial of 5:  120 
# Iterative factorial of 10:  3628800 
# Recursive factorial of 10:  3628800 
# math.factorial of 10:  3628800 
# Iterative factorial of 15:  1307674368000 
# Recursive factorial of 15:  1307674368000 
# math.factorial of 15:  1307674368000 
 
 

Python - Finding GCD with Euclids Algorithm

# Implementing the Euclidean Algorithm
# is simple in python.
#
# Euclid's algorithm is used to efficiently
# find two numbers greatest common divisor (GCD)
 
# Division based Euclidean algorithm
def gcd(a,b):
    while b != 0:
        temp = b
        b = a%b
        a = temp
    return a
 
# Recursive based Euclidean algorithm
def recursiveGCD(a,b):
    if b==0:
        return a
    else:
        return recursiveGCD(b, a%b)
 
 
# just to prove they both work the same:
def findGCD(a,b):
    divisionStyle = gcd(a,b)
    recursiveStyle = recursiveGCD(a,b)
    if divisionStyle != recursiveStyle:
        return "Fail...GCDs differ"
    else:
        return divisionStyle
 
print findGCD(1071, 462)
print findGCD(5, 10)
print findGCD(5214, 24324)
 
# my output:
#   21
#   5
#   6
 
 
 

Python - the final countdown

# There is more than one way to accomplish a task. 
# I needed a method to countdown from a positive 
# number down to 0.  Here are three ways to solve 
# the issue.  Of course there are many more possible 
# solutions. 
# 
# I'd like to title this post "The Final Count Down" 
# Listen to this tune whilst perusing the script: 
# www.youtube.com/watch?v=tt_ro2aerQg 
 
 
# Using recursion always makes the girls swoon. 
def recursiveCountdown(number):
    print number
    if number > 0:
        recursiveCountdown(number-1)
 
# Old school while loop.  This solution gets points 
# for being the most obvious. 
def whileLoopCountdown(number):
    while number > -1:
        print number
        number -= 1
 
# Using python's xrange function is the most concise. 
def xrangeCountdown(number):
    for i in xrange(number, -1, -1):
        print i
 
print "It's the final countdown" 
number = input("Enter number: ")
 
print "Recursive..." 
recursiveCountdown(number)
print "While Loop..." 
whileLoopCountdown(number)
print "xrange..." 
xrangeCountdown(number)
 
 
# my output: 
# 
#It's the final countdown 
#Enter number: 5 
#Recursive... 
#5 
#4 
#3 
#2 
#1 
#0 
#While Loop... 
#5 
#4 
#3 
#2 
#1 
#0 
#xrange... 
#5 
#4 
#3 
#2 
#1 
#0