chapter7 python 字典

python字典，用{}定义，是多组对相关联的键、值对。

1.创建字典，通过键访问字典

#访问字典的值，指定字典名与键：
people = {'color':'yellow','point':5}
print(people['color'])

out：
yellow

2.通过键修改字典值

#修改字典中值
people['color'] = 'black'
print(people['color'])
out：black

3.遍历字典

#遍历字典（不关注存储顺序，只关注键-值关联关系）
for key, value in people.item():
#遍历键
for key in people.key():
#按顺序遍历键
for key in sorted(people.key()):
#遍历值
for value in people.value():
#遍历不同值
for value in set(people.value()):

4.嵌套，列表中存字典、字典中存列表，字典中存字典

#嵌套，列表中存字典，list = [字典1，字典2，字典3]
peoples = []  #通过for循环为列表内添加字典
for people_number in range(30):
    new_people = {'color':'yellow','point':5}
peoples.append(new_people)

#字典中存列表（一个key关联多个值）
dict1 = {'key1':'value1','key2':['zhao','qian','sun']}

#字典中存字典，
dict2={'key1':'{'key11':'value11','key12','value12'},
       'key2':'{'key21':'value21' ,'key22':'value22'}}