# factorial program
n = int(input())
fact = 1
for i in range(n,1,-1):      #line4 #  this line print the range in reverce
    fact = fact*i
print(fact)

some explain the line4. how is the for loop printing the n in reverse?

CodePudding user response：

The 3 main parameters of the range() function are start, stop and step. If you start at n to stop on 1 and decrease the index variable by 1 unit every time the loop executes, it will loop the values in reverse order.

For example:

n=10
for i in range(n,1,-1):
    print(i)

This loop will start at i=10, as you can see from the step value, it will decrease its value by 1 until reach the stop value (exclusive), in this case, 1 too. So the output will be:

10
9
8
7
6
5
4
3
2