Python -- 遍历字典时删除元素报异常

错误的代码①

d = {'a':1, 'b':0, 'c':1, 'd':0}
for key, val in d.items():
    del(d[k])

错误的代码② -- 对于Python3

d = {'a':1, 'b':0, 'c':1, 'd':0}
for key, val in d.keys():
    del(d[k])

正确的代码

d = {'a':1, 'b':0, 'c':1, 'd':0}
keys = list(d.keys())
for key, val in keys:
    del(d[k])