python dict

初始化

构造方法创建

d = dict()
d = dict(name="nico", age=23)
d = dict((['name', "nico"], ['age', 23]))

 当然还有更方便，简单的

d = {}
d = {"name":"nico", "age":23}

 

 

遍历

通过对key的遍历，遍历整个dict

 

d = {"name":"nico", "age":23}
for key in d:
    print "key=%s, value=%s" % (key, d[key])
    
for key in d.iterkeys():
    print "key=%s, value=%s" % (key, d[key])
    
for key in d.keys():
    print "key=%s, value=%s" % (key, d[key])
    
for key in iter(d):
    print "key=%s, value=%s" % (key, d[key])
    
for key,item in d.items():
    print "key=%s, value=%s" % (key, item)

 

 当然也可以直接遍历value

 

d = {"name":"nico", "age":23}
for value in d.values():
    print value
    
for key,value in d.viewitems():
    print "key=%s, value=%s" % (key, value)

for value in d.viewvalues():
    print "value=%s" % (value)

这里values和viewvalues的区别

 

后者返回的是该字典的一个view对象，类似数据库中的view，当dict改变时，该view对象也跟着改变

 

常用方法

 

d = {"name":"nico", "age":23}
d["name"] = "aaaa"
d["address"] = "abcdefg...."
print d   #{'age': 23, 'name': 'aaaa', 'address': 'abcdefg....'}

 

 

获取dict值

print d["name"]               #nico
print d.get("name")         #nico

 

 如果key不在dict中，返回default，没有为None

print d.get("namex", "aaa")       #aaa
print d.get("namex")                  #None

 

 

排序sorted()

d = {"name":"nico", "age":23}
for key in sorted(d):
    print "key=%s, value=%s" % (key, d[key])
#key=age, value=23
#key=name, value=nico

 

 

删除del

d = {"name":"nico", "age":23}

del d["name"]
#如果key不在dict中，抛出KeyError
del d["names"]

Traceback (most recent call last):
  File "F:\workspace\project\pydev\src\ddd\ddddd.py", line 64, in <module>
    del d["names"]
KeyError: 'names'

 

 

清空clear()

d = {"name":"nico", "age":23}
d.clear()
print d                                                    #{}

 

copy()

d1 = d.copy()               #{'age': 23, 'name': 'nico'}
#使用返回view对象
d2 = d1.viewitems()    #dict_items([('age', 23), ('name', 'nico')])
#修改字典d1，新增元素
d1["cc"] = "aaaaaa" 
print d2                 
#dict_items([('cc', 'aaaaaa'), ('age', 23), ('name', 'nico')])

 

 

pop(key[, default])

如果key在dict中，返回，不在返回default

#如果key在dict中，返回，不在返回default
print d.pop("name", "niccco")                #nico
print d.pop("namezzz", "niccco")           #niccco
#key不在dict中，且default值也没有，抛出KeyError
print d.pop("namezzz")                         #此处抛出KeyError

 

popitem()

删除并返回dict中任意的一个(key,value)队，如果字典为空会抛出KeyError

d = {"name":"nico", "age":23}
print d.popitem()       #('age', 23)
print d.popitem()       #('name', 'nico')
#此时字典d已为空
print d.popitem()      #此处会抛出KeyError

 

update([other])

将字典other中的元素加到dict中，key重复时将用other中的值覆盖

d = {"name":"nico", "age":23}
d2 = {"name":"jack", "abcd":123}
d.update(d2)
print d     #{'abcd': 123, 'age': 23, 'name': 'jack'}