Can someone help explain this python recursive code?

Question

I am trying to sort a stack such that the smallest elements are on the top of the stack using recursion. When I run the code, the result is sometimes unpredictable.

Here is the code

class stack:
def __init__(self):
    self.items = []
def push(self, item):
    self.items.append(item)
def pop(self):
    return self.items.pop()
def peek(self):
    return self.items[len(self.items)-1]
def is_empty(self):
    return self.items == []
def size(self):
    return len(self.items)

class sort_the_stack:

    def __init__(self):
        self.sorted_stack = stack()

    def sort_stack(self, new_stack):
        for i in range(new_stack.size()):
            self.push(new_stack.pop())
        return self.sorted_stack

    def push(self, val):
        if self.sorted_stack.size() == 0:
            self.sorted_stack.push(val)
        else:
            temp = self.sorted_stack.peek()
            if val < temp:
                self.sorted_stack.push(val)
            else:
                temp = self.sorted_stack.pop()
                self.push(temp)
                self.sorted_stack.push(temp)

    def peek(self):
        return self.sorted_stack.peek()

    def pop(self):
        return self.sorted_stack.pop()

new_stack = stack()

new_stack.push(10)

new_stack.push(2)

new_stack.push(1)

new_stack.push(8)

new_stack.push(10)

new_stack.push(10)

stack1 = sort_the_stack()

stack1.sort_stack(new_stack)


print(stack1.pop())

print(stack1.pop())

print(stack1.pop())

print(stack1.pop())

print(stack1.pop())

print(stack1.pop())

Answer 1

In your recursive case, it looks like you're pushing the temp value twice, instead of the value you're actually trying to add. You have

else:
 temp = self.sorted_stack.pop()
 self.push(temp)
 self.sorted_stack.push(temp)

but I think you want

else:
 temp = self.sorted_stack.pop()
 self.push(val)
 self.sorted_stack.push(temp)