Python.. output is 5. I cannot figure out how to step through this recursive function in my head and get it. Help?

Question

def fb(n):
if n==0
return 0
if n==1:
return 1
else:
return(fb(n-1)+fb(n-2))
print(fb(5))

Answer 1

fb(0) == 0
fb(1) == 1
fb(n) == fb(n-1) + fb(n-2) for n > 1

fb(5)
== fb(4) + fb(3)
== fb(3) + fb(2) + fb(2) + fb(1)
==fb(2) + fb(1) + fb(1) + fb(0) + fb(1) + fb(0) + fb(1)
== fb(1) + fb(0) + fb(1) + fb(1) + fb(0) + fb(1) + fb(0) + fb(1)
== 1 + 0 + 1 + 1 + 0 + 1 + 0 + 1
== 5

Answer 2

Thank you Diego Acero!