Understanding recursive string reversal

Question

I\'m using the Python Tutorial visualize webpage to try and understand the flow of this function that reverses a string:

text = \"hello\"
def reverse(text):
            


        

Answer 1

Here's the sequence of recursive calls, and what they return. You'll see that reverse("hello") returns the result of reverse("ello") plus "h".

reverse("hello")
  --> return reverse("ello") + "h"

So then the question is what does reverse("ello") return?

reverse("ello")
  --> return reverse("llo") + "e"

Continuing on...

reverse("llo")
  --> return reverse("lo") + "l"

reverse("lo")
  --> return reverse("o") + "l"

Finally, it bottoms out when reverse("o") is called. Here len(text) <= 1, and so it returns simply "o".

reverse("o")
  --> return "o"

You can then work your way back up from bottom to top to calculate the return value from the original reverse("hello") call.

Answer 2

reverse("hello")
-> reverse("ello") + "h"
-> reverse("llo") + "e" + "h"
-> reverse("lo") + "l" + "e" + "h"
-> reverse("o") + "l" + "l" + "e" + "h"
-> "o" + "l" + "l" + "e" + "h"
-> "olleh"

This is to show the purpose of the return reverse(text[1:]) + text[0] line and its behaviour in action.