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Python

Posted by Jason Ladieu
Jason Ladieu
10,635 Points

I've been giving over this function for a day and I can't seem to work out how it is working. Would someone kindly help?

Would someone help a newbie explain what is going on in detail? Thanks!!

def recursive(depth):
    depth+=1
    while (depth < 5):
        ret = recursive(depth)
    return depth

ret = recursive(0)
print("the recursive depth is ", ret)

1 Answer

james south
.a{fill-rule:evenodd;}techdegree seal-36
james south
Front End Web Development Techdegree Graduate 33,271 Points

it's a recursive function that calls itself in the body. this creates what is sometimes called a stack of recursive function calls. the stack ends when what is called the base case is reached, and then the function moves back up through the stack and returns the result. there is nothing wrong with this, a common example is computing factorials or fibonacci numbers, but this particular function does not have a base case and therefore causes an infinite loop. the depth variable counts up to 5 and creates a stack of depth 5, and at 5 it skips the while loop and returns 5, but the next step is to move back up through the stack. in the previous level, depth is still 4. 4 is less than 5, so it enters the while loop, the function is called on 4, 1 is added to 4 to make 5, 5 skips the while loop and is returned, and on and on it goes.

Jason Ladieu
Jason Ladieu
10,635 Points

A ha! Thank you so much for the clarification. That one has been bugging me.