Recursion in python need help understanding-CodePudding

i need help understanding this recursion thing i am new to coding and trying to learn python

def tri_recursion(k):
    if(k > 0):
        result = k   tri_recursion(k - 1)
        print(result)
    else:
        result = 0
    return result

print("\n\nRecursion Example Results")
tri_recursion(6)
 
Recursion Example Results
1
3
6
10
15
21

i understood 1 and 3 i never understand why the answer is 6 by the third row because result = 3 tri_recursion(3-1) print(result) which is 5 right ?

CodePudding user response：

It may help to print out k with your result

def tri_recursion(k):
    if(k > 0):
        result = k   tri_recursion(k - 1)
        print(f"k: {k} = {result}")
    else:
        result = 0
    return result

print("\n\nRecursion Example Results")
tri_recursion(6)

produces

Recursion Example Results
k: 1 = 1
k: 2 = 3
k: 3 = 6
k: 4 = 10
k: 5 = 15
k: 6 = 21

So you can see for each k that it is itself the result from the previous line.

CodePudding user response：

Here's how it works:

tri_recursion(1): result = k = 1

tri_recursion(2): result = k tri_recursion(2-1) = k tri_recursion(1) = 2 1 = 3

tri_recursion(3): result = k tri_recursion(3-1) = k tri_recursion(2) = 3 3 = 6

... and so on

Hope it helps!