难道不是一行一行地执行python代码？

Question

这是错误：UnboundLocalError：赋值之前引用了本地变量'eggs'

def spam():
    print(eggs)
    eggs = "spam local"

eggs = "global"
spam()

如果逐行执行，鸡蛋的值不应该等于打印的“全局”值吗？