python字典（dictionary）使用：不常用的基本函数例子

浏览数：25 / 时间：2015年06月08日

python字典dictionary，以前有过介绍，现就几个不常用函数写测试例子，

字典声明如，a={};

[python]dictionary方法说明：参考：http://blog.csdn.net/wangran51/article/details/8440848

Operation	Result	Notes
`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`	(1), (10)
`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`	(1)
`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`	(2)
`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`	(2)
`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	(3)
`a.keys()`	a copy of `a`‘s list of keys 得到键的list	(3)
`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`	(9)
`a.fromkeys(seq[, value])`	Creates a new dictionary with keys from `seq` and values set to `value`	(7)
`a.values()`	a copy of `a`‘s list of values	(3)
`a.get(k[, x])`	`a[k]` if `k in a`, else `x`	(4)
`a.setdefault(k[, x])`	`a[k]` if `k in a`, else `x` (also setting it)	(5)
`a.pop(k[, x])`	`a[k]` if `k in a`, else `x` (and remove k)	(8)
`a.popitem()`	remove and return an arbitrary (`key`, `value`) pair	(6)
`a.iteritems()`	return an iterator over (`key`, `value`) pairs	(2), (3)
`a.iterkeys()`	return an iterator over the mapping‘s keys	(2), (3)
`a.itervalues()`	return an iterator over the mapping‘s values	(2), (3)

测试code：

[wizad@sr104 lmj]$ vim test.py
dict = {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}
for k in dict:
print "dict[%s]="%k,dict[k]

key="c"
if "c" not in dict:
print "it is not in %s" %key

print "-------------"
print dict.items()
print dict.keys()
print dict.values()

print "-------------"
iter = dict.iteritems()
for it in iter:
print "iteritems is:",it
print type(it)

print "-------------"
key_iter = dict.iterkeys()
for ki in key_iter:
print "key_iter is",ki
print type(ki)

print "-------------"
val_iter = dict.itervalues()
for vi in val_iter:
print "val_iter is",vi
print type(vi)
print "-------------"

结果：

dict[a]= apple
dict[b]= banana
dict[o]= orange
dict[g]= grape
it is not in c
-------------
[(‘a‘, ‘apple‘), (‘b‘, ‘banana‘), (‘o‘, ‘orange‘), (‘g‘, ‘grape‘)]
[‘a‘, ‘b‘, ‘o‘, ‘g‘]
[‘apple‘, ‘banana‘, ‘orange‘, ‘grape‘]
-------------
iteritems is: (‘a‘, ‘apple‘)
<type ‘tuple‘>
iteritems is: (‘b‘, ‘banana‘)
<type ‘tuple‘>
iteritems is: (‘o‘, ‘orange‘)
<type ‘tuple‘>
iteritems is: (‘g‘, ‘grape‘)
<type ‘tuple‘>
-------------
key_iter is a
<type ‘str‘>
key_iter is b
<type ‘str‘>
key_iter is o
<type ‘str‘>
key_iter is g
<type ‘str‘>
-------------
val_iter is apple
<type ‘str‘>
val_iter is banana
<type ‘str‘>
val_iter is orange
<type ‘str‘>
val_iter is grape
<type ‘str‘>
-------------

此外还有：

#字典的update：合并两个字典，无序
dict = {"a" : "apple", "b" : "banana"}
print dict
dict2 = {"c" : "grape", "d" : "orange"}
dict.update(dict2)
print dict
#udpate()的等价语句
D = {"key1" : "value1", "key2" : "value2"}
E = {"key3" : "value3", "key4" : "value4"}
for k in E:
D[k] = E[k]
print D

输出：

{‘key3‘: ‘value3‘, ‘key2‘: ‘value2‘, ‘key1‘: ‘value1‘, ‘key4‘: ‘value4‘}

#设置默认值

dict = {}
dict.setdefault("a")
print dict
dict["a"] = "apple"
dict.setdefault("a","default")
print dict

#调用sorted()排序
dict = {"a" : "apple", "b" : "grape", "c" : "orange", "d" : "banana"}
print dict
#按照key排序
print sorted(dict.items(), key=lambda d: d[0])
#按照value排序
print sorted(dict.items(), key=lambda d: d[1])

#字典的浅拷贝
dict = {"a" : "apple", "b" : "grape"}
dict2 = {"c" : "orange", "d" : "banana"}
dict2 = dict.copy()
print dict2

#字典的深拷贝
import copy
dict = {"a" : "apple", "b" : {"g" : "grape","o" : "orange"}}
dict2 = copy.deepcopy(dict)
dict3 = copy.copy(dict)
dict2["b"]["g"] = "orange"
print dict
dict3["b"]["g"] = "orange"
print dict

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python字典（dictionary）使用：不常用的基本函数例子