一行上的Python变量分配

Question

为什么这样做：

def make_fib():
    cur, next = 0, 1
    def fib():
        nonlocal cur, next
        result = cur
        cur, next = next, cur + next
        return result
    return fib

工作方式不同于：

def make_fib():
    cur, next = 0, 1
    def fib():
        nonlocal cur, next
        result = cur
        cur = next
        next = cur + next
        return result
    return fib

我看到第二个怎么弄乱了，因为在cur = next和next = cur + next时，因为本质上它将变成next = next + next，但是第一个为什么运行不同？

Answer 1

cur, next = next, cur + next

与以下操作相同：

# right-hand side operations
tmp_1 = next
tmp_2 = cur + next

# assignment
cur = tmp_1
next = tmp_2

因为对右侧进行了充分评估，然后将值分配给左侧