python语言key_Python语言学习:字典常用的方法
1. 增加:字典[key]=value(不存在的key和value)
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
info['stu1104']='crystal'
print(info) #輸出結(jié)果:{'stu1101': 'TengLan', 'stu1102': 'LuoZe', 'stu1103': 'XiaoZe', 'stu1104': 'crystal'}
2. 修改:字典[key]=value(已存在的key,修改對(duì)應(yīng)value)
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
info['stu1101']='crystal'
print(info) #輸出結(jié)果:{'stu1101': 'crystal', 'stu1102': 'LuoZe', 'stu1103': 'XiaoZe'}
3. 刪除
a. 字典.pop(key)
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
info.pop("stu1101")
print(info) #{'stu1102': 'LuoZe', 'stu1103': 'XiaoZe'}
b. del 字典[key]
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
del info['stu1101']
print(info)
4. 查找
a. in:如果key存在,返回true;反之返回false
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
print("stu1101" in info) #輸出結(jié)果:True
b.get:通過key獲取到value,如果不存在返回None
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
print(info.get("stu1101")) #輸出結(jié)果:TengLan
c. 字典[key]:如果key存在,返回value;反之則報(bào)錯(cuò)
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
print(info["stu1104"])
#輸出結(jié)果:KeyError: 'stu1104'
5. 多級(jí)字典嵌套操作
av_catalog = {
"Europe":{
"Germany":["地域廣","文化濃郁"],
"United Kingdom":["歷史古國(guó)","高校多"],
"Italy":["異域風(fēng)情","人美"],
"Belgium":["時(shí)裝","文化"]
},
"Japan":{
"tokyo":["美食","旅游"]
},
"China":{
"Beijing":["國(guó)都","歷史悠久"]
}
}
av_catalog["China"]["Beijing"][1]="文明之源"
print(av_catalog) #輸出結(jié)果:{'Europe': {'Germany': ['地域廣', '文化濃郁'], 'United Kingdom': ['歷史古國(guó)', '高校多'], 'Italy': ['異域風(fēng)情', '人美'], 'Belgium': ['時(shí)裝', '文化']}, 'Japan': {'tokyo': ['美食', '旅游']}, 'China': {'Beijing': ['國(guó)都', '文明之源']}}
6. setdefault :創(chuàng)建新的key-value
av_catalog = {
"Europe":{
"Germany":["地域廣","文化濃郁"],
"United Kingdom":["歷史古國(guó)","高校多"],
"Italy":["異域風(fēng)情","人美"],
"Belgium":["時(shí)裝","文化"]
},
"Japan":{
"tokyo":["美食","旅游"]
},
"China":{
"Beijing":["國(guó)都","歷史悠久"]
}
}
av_catalog.setdefault("Taiwan",{"travel":[1,2]})
print(av_catalog)
#輸出結(jié)果:{'Europe': {'Germany': ['地域廣', '文化濃郁'], 'United Kingdom': ['歷史古國(guó)', '高校多'], 'Italy': ['異域風(fēng)情', '人美'], 'Belgium': ['時(shí)裝', '文化']}, 'Japan': {'tokyo': ['美食', '旅游']}, 'China': {'Beijing': ['國(guó)都', '歷史悠久']}, 'Taiwan': {'travel': [1, 2]}}
7. update:兩個(gè)字典合并,有交叉合并,如沒有交叉就更新
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
b = {
'stu1101':"crystal",
1:3,
2:5
}
info.update(b)
print(info) #輸出結(jié)果:{'stu1101': 'crystal', 'stu1102': 'LuoZe', 'stu1103': 'XiaoZe', 1: 3, 2: 5}
8. fromkeys:初始化一個(gè)新的字典
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
b = {
'stu1101':"crystal",
1:3,
2:5
}
c = info.fromkeys([6,7,8],"test")
print(c) #輸出結(jié)果:{6: 'test', 7: 'test', 8: 'test'}
9. items:把字典轉(zhuǎn)換成列表
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
print(info.items())
#輸出結(jié)果:dict_items([('stu1101', 'TengLan'), ('stu1102', 'LuoZe'), ('stu1103', 'XiaoZe')])
10. 字典循環(huán)
info={
'stu1101':'TengLan',
'stu1102':'LuoZe',
'stu1103':'XiaoZe'
}
for i in info: #此方式循環(huán)高效
print(i,info[i])
for k,v in info.items(): #此方式不適合數(shù)據(jù)量較大的情況
print(k,v)
#輸出結(jié)果:
stu1101 TengLan
stu1102 LuoZe
stu1103 XiaoZe
stu1101 TengLan
stu1102 LuoZe
stu1103 XiaoZe
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