python的字典错误：RuntimeError: dictionary changed size during iteration

1.在字典遍历过程中修改字典元素，报错 RuntimeError: dictionary changed size during iteration

错误代码：

for i in phone:
    i = int(i)
    for key in dict_phone.keys():
        if key == i:
            print(dict_phone.pop(key,'ss'))

改正

for i in phone:
    i = int(i)
    for key in list(dict_phone.keys()):
        if key == i:
            print(dict_phone.pop(key,'ss'))