Learning notes for Python/002-5 (2018-5-21)

dictionaries and their operations
The dictionary is used to store the two corresponding keys and values, that is, the dict type; When a dictionary is created, each key is used to get the corresponding value, and the key in the dictionary cannot be duplicated; it is characterized by a Key-value key value type, unordered, and no subscript can be found by subscript.
(1) Dictionary replacement, add, delete, find

infor={    ‘2014132001‘:"DiaoCan",    ‘2014132002‘:"DaQiao",    ‘2014132003‘:"HuanhYueYing"}print(infor)infor[‘2014132002‘]=‘XiaoQiao‘      # 替换print(infor)infor[‘2014132089‘]=‘wuzhetain‘    # 添加print(infor)# del infor[‘2014132089‘]     # 删除#infor.popitem()     # 随机删除infor.pop (‘2014132089‘)print(infor)print(infor[‘2014132001‘])   # 查找print(infor.get(‘2014132001‘) )  #  更为安全的查找,当键不存在的时候不会报错print(‘2014132001‘ in infor)   #  查某是否存在，返回的是布尔类型

(2) Updating of dictionaries

infor={    ‘2014132001‘:"DiaoCan",    ‘2014132002‘:"DaQiao",    ‘2014132003‘:"HuanhYueYing"}print(infor)a={    ‘2014132001‘:‘LuBu‘,    ‘2014132004‘:‘Guanyu‘,    ‘2014132005‘:‘Dongzhuo‘}infor.update(a)   # 有的就更新，没有的就添加print(infor)

(3) Conversion and extension of dictionaries

infor={    ‘2014132001‘:"DiaoCan",    ‘2014132002‘:"DaQiao",    ‘2014132003‘:"HuanhYueYing"}print(infor)print(infor.items() )   # 将字典转化为列表b=dict.fromkeys([1,2,3,4],[1,{‘name‘:‘zhangfei‘},‘Zhaoyun‘])  # 这里要注意的就是1，2，3，4所对应的值是同一个print(b)b[2][1][‘name‘]=‘Xiahoudun‘print(b)

(4) Output of the dictionary

infor={    ‘2014132001‘:"DiaoCan",    ‘2014132002‘:"DaQiao",    ‘2014132003‘:"HuanhYueYing"}print(infor)for i in infor:     # 建议使用这个    print(i,infor[i])for k,v in infor.items():  # 多了一步转换为列表    print(k,v)

(5) Multilevel specified nesting

Site_of_world={    ‘American‘:{        ‘www.barrett.net‘:["Barrett Firearms Manufacturing","巴雷特×××公司"],        ‘sands.com‘:["Las Vegas Sands","拉斯×××金沙集团 "],        ‘www.omnicomgroup.com‘:["Omnicom Group","奥米康集团"],        ‘www.wyethnutrition.com.hk ‘:["Wyeth","惠氏"]    }    ,    ‘Japan‘:{        ‘www.unicharm.com.cn‘:["Unicharm Group","尤妮佳集团"],        ‘www.klab.com/cn‘:["KLab","可来"]    }    ,    ‘Chain‘:{        ‘hknd-group.com/cn/‘:["HKND Group","HKND集团"],        ‘www.eegmusic.com‘:["Emperor Entertainment","英皇娱乐"]    }}print(Site_of_world.keys())print(Site_of_world.values())print(Site_of_world)Site_of_world.setdefault(‘Chain‘,{‘www.baidu.com‘:"百度 "})  # 键存在的情况下，不改变value的值print(Site_of_world)Site_of_world.setdefault(‘South Korea‘,{‘www.smtown.com‘:"SM娱乐"}) # 键不存在的情况下，创建新的key-valueprint(Site_of_world)

Learning notes for Python/002-5 (2018-5-21)