Python Dict用法

浏览数：37 / 时间：2015年06月08日

Operation	Result
`len(a)`	the number of items in `a 得到字典中元素的个数`
`a[k]`	the item of `a` with key `k 取得键K所对应的值`
`a[k] = v`	set `a[k]` to `v 设定键k所对应的值成为v`
`del a[k]`	remove `a[k]` from `a 从字典中删除键为k的元素`
`a.clear()`	remove all items from `a 清空整个字典`
`a.copy()`	a (shallow) copy of `a 得到字典副本`
`k in a`	`True` if `a` has a key `k`, else `False 字典中存在键k则为返回True，没有则返回False`
`k not in a`	Equivalent to `not` `k` in `a` `字典中不存在键k则为返回true,反之返回False`
`a.has_key(k)`	Equivalent to `k` `in` `a`, use that form in new code 等价于k in a
`a.items()`	a copy of `a`‘s list of (`key`, `value`) pairs 得到一个键，值的list
`a.keys()`	a copy of `a`‘s list of keys 得到键的list
`a.update([b])`	updates (and overwrites) key/value pairs from `b从b字典中更新a字典，如果键相同则更新，a中不存在则追加`
`a.fromkeys(seq[, value])`	Creates a new dictionary with keys from `seq` and values set to `value`
`a.values()`	a copy of `a`‘s list of values
`a.get(k[, x])`	`a[k]` if `k in a`, else `x`
`a.setdefault(k[, x])`	`a[k]` if `k in a`, else `x` (also setting it)
`a.pop(k[, x])`	`a[k]` if `k in a`, else `x` (and remove k)
`a.popitem()`	remove and return an arbitrary (`key`, `value`) pair
`a.iteritems()`	return an iterator over (`key`, `value`) pairs
`a.iterkeys()`	return an iterator over the mapping‘s keys
`a.itervalues()`	return an iterator over the mapping‘s values