python中集合为什么不可以.pop(0)但可以.pop()

Question

sandwich_orders = ['niurou','zhurou','pas','rabbit','pas','apple','banana','pas']
print("--- pas is not in ---")
'''while 'pas' in sandwich_orders:
sandwich_orders.remove('pas')'''
sandwich_orders = set(sandwich_orders)
sandwich_orders.remove('pas')
finishied_sandwich = []
while sandwich_orders :
finish = sandwich_orders.pop(0)

print(f"I have finished {finish}")
finishied_sandwich.append(finish)

print(sandwich_orders)
print(finishied_sandwich)

学习练习遇到的问题，求解答

Answer 1

集合是可变的、无序的、元素唯一的结构
既然它无序，那么你就不能用索引访问，也不可切片
所以pop后面不可带索引定位，虽然是删除，但它也是随机删除