Logic behind the Inner Function

Question

I'm currently learning Python and following a tutorial and made it to decorators. But before diving there, i want to get a good grasp of how inner function works and I came across this piece of code.

def max(a, b, c):
    def max2(x, y):     
        return x if x >= y else y   
    return max2(a, max2(b, c))

main_max = max(15, 5, 10)

print(main_max)

Now, I'm trying to understand the logic behind it, but I can't seem to understand the sequence of passing the arguments. I ran it on debug mode and did the lines step-by-step and what I noticed was x is being assigned the value of b and y is being assigned the value of c. Why is that?

Is it because the second argument which is max2(b, c) is being evaluated first before evaluating max2(a, max2(b, c)) ?

Answer 1

Max takes three arguments. Max2 takes two arguments. The only relevant line of code is

return max2(a, max2(b, c))

We know that a is a. In order to continue the computation we need to resolve (using max2) the greater of b or c. In other words, max2(15, max2(5, 10)) can be thought of like

t = max2(5, 10) # (5 ? 10) = 10
return max2(15, t) # (15 ? 10) = 15

The only other thing to realize is that the scope of max2 is being limited to within max.