new post draft

Author: amitsaha

content/trailing-zeros-factorial-python.rst

@@ -6,6 +6,7 @@ Number of trailing zeros in the factorial of an integer
 :slug: trailing-zeros-factorial
 :summary: Use Python to find the number of trailing zeros in the factorial of an integer
 
+Please note, the math expressions are broken. I will be fixing it soon.
 
 Hi all, I recently learned about a cool formula to calculate the number of
 trailing zeros in the factorial of a number. It has been a while since I 
@@ -35,4 +36,45 @@ The key bit there in is this formula:
 
 where, ``n`` is the number for whose factorial we want to find the number of trailing zeros in and ``k`` 
 
+The following Python program implements the above formula:
+
+.. code::
+
+        import math
+
+
+	def is_positive_integer(x):
+	    try:
+		x = float(x)
+	    except ValueError:
+		return False
+	    else:
+		if x.is_integer() and x > 0:
+		    return True
+		else:
+		    return False
+
+
+	def trailing_zeros(num):
+	    if is_positive_integer(num):
+		# The above function call has done all the sanity checks for us
+		# so we can just convert this into an integer here
+		num = int(num)
+
+		k = math.floor(math.log(num, 5))
+		zeros = 0
+		for i in range(1, k + 1):
+		    zeros = zeros + math.floor(num/math.pow(5, i))
+		return zeros 
+	    else:
+		print("Factorial of a non-positive integer is undefined")
+
+
+	if __name__ == "__main__":
+	    fact_num = input(
+		"Enter the number whose factorial's trailing zeros you want to find: "
+	    )
+	    num_zeros = trailing_zeros(fact_num)
+	    print("Number of trailing zeros: {0}".format(num_zeros))
+