python字典元素的删除

py在遍历字典的时候，一般的有涉及到满足条件则删除该元素

办法1：

a = {"a": "1", "b": "2"}for k,v in  a.items():if k == "b":    del a[k]    print a# {'a': '1'}

办法2：

a = {"a": "1", "b": "2"}f = filter(lambda i: i[0] != "b" , a.items())print f# [('a', '1')]print a#{'a': '1', 'b': '2'}

错误的用法是用迭代器遍历的时候删除如：

>>> a = {"a": "1", "b": "2"}>>> for i in  a:del a[i]Traceback (most recent call last):  File "<pyshell#50>", line 1, in <module>    for i in  a:RuntimeError: dictionary changed size during iteration