Python Dict用法

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python dictionary方法说明

2007-05-19 23:24

申明 m={};

[python]dictionary方法说明

2007-03-13 18:10

OperationResultNoteslen(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] = vset 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 aTrue 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 aEquivalent 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)

#字典的添加、删除、修改操作
dict = {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}
dict["w"] = "watermelon"
del(dict["a"])
dict["g"] = "grapefruit"
print dict.pop("b")
print dict
dict.clear()
print dict

#字典的遍历
dict = {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}
for k in dict:
print "dict[%s] =" % k,dict[k]

#字典items()的使用
dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}
#每个元素是一个key和value组成的元组，以列表的方式输出
print dict.items()

#调用items()实现字典的遍历
dict = {"a" : "apple", "b" : "banana", "g" : "grape", "o" : "orange"}
for (k, v) in dict.items():
print "dict[%s] =" % k, v

#调用iteritems()实现字典的遍历
dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}
print dict.iteritems()
for k, v in dict.iteritems():
    print "dict[%s] =" % k, v
for (k, v) in zip(dict.iterkeys(), dict.itervalues()):
    print "dict[%s] =" % k, v

#使用列表、字典作为字典的值
dict = {"a" : ("apple",), "bo" : {"b" : "banana", "o" : "orange"}, "g" : ["grape","grapefruit"]}
print dict["a"]
print dict["a"][0]
print dict["bo"]
print dict["bo"]["o"]
print dict["g"]
print dict["g"][1]

dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}
#输出key的列表
print dict.keys()
#输出value的列表
print dict.values()
#每个元素是一个key和value组成的元组，以列表的方式输出
print dict.items()

dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}
it = dict.iteritems()
print it

#字典中元素的获取方法
dict = {"a" : "apple", "b" : "banana", "c" : "grape", "d" : "orange"}
print dict
print dict.get("c", "apple")
print dict.get("e", "apple")
#get()的等价语句
D = {"key1" : "value1", "key2" : "value2"}
if "key1" in D:
    print D["key1"]
else:
    print "None"

#字典的更新
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
#字典E中含有字典D中的key
D = {"key1" : "value1", "key2" : "value2"}
E = {"key2" : "value3", "key4" : "value4"}
for k in E:
D[k] = E[k]
print D

#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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