接下來介紹字典
,這在未來工作上,會是很常使用的,就來好好了解一下唄…
字典是一個 key(鍵)-value(值)
的數據類型,可以儲存很多訊息
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
---------------執行結果---------------
{'stu1001': 'Tony Stark', 'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers'}
Process finished with exit code 0
觀察一下,有發現什麼了嗎?沒錯,字典怎麼沒有按照順序排列呢?
字典的其中一個特性是無順序性的
,因為沒有下標
,所以不會照順序排列,但仍然可以透過key
來查找,字典不像列表是有下標的
,可以透過下標來查找位置,先試試用key
來查找Tony Stark
,查找有二種方法
Method 1:
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
print(info["stu1001"]) # 這種查找方式是要百分百確定key有存在於字典的,否則會報錯
print(info)
---------------執行結果---------------
{'stu1001': 'Tony Stark', 'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers'}
Tony Stark
Process finished with exit code 0
Method 2:dict.get()
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
print(info.get('stu1001')) # 比較安全查找的方式
print(info.get('stu1004')) # 故意查找不存在的,只會返回none
---------------執行結果---------------
{'stu1001': 'Tony Stark', 'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers'}
Tony Stark
None
Process finished with exit code 0
那有沒有一個方法,可以判斷我的字典
裡,這個數據存不存在?存在就取值,不存在就建立
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
print('stu1003' in info) # Pyhton2.7版,會寫 info.has_key('stu1003'),效果是一樣的
print('stu1004' in info)
---------------執行結果---------------
{'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers', 'stu1001': 'Tony Stark'}
True
False
Process finished with exit code 0
再把 Tony Stark
改成 東尼史塔克
,看看要怎麼修改…
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
info["stu1001"] = "東尼史塔克"
print(info)
---------------執行結果---------------
{'stu1001': 'Tony Stark', 'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers'}
{'stu1001': '東尼史塔克', 'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers'}
Process finished with exit code 0
那再新增一個人員進來呢?
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
info["stu1001"] = "東尼史塔克"
info["stu1004"] = "復仇者聯盟"
print(info)
---------------執行結果---------------
{'stu1002': 'Steve Rogers', 'stu1003': 'Bruce Banner', 'stu1001': 'Tony Stark'}
{'stu1004': '復仇者聯盟', 'stu1002': 'Steve Rogers', 'stu1003': 'Bruce Banner', 'stu1001': '東尼史塔克'}
Process finished with exit code 0
那要在刪除字典中,不想要的資料,要怎麼刪除呢? 總共有三種方法
Method 1:del
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
#print(info["stu1001"])
info["stu1001"] = "東尼史塔克"
info["stu1004"] = "復仇者聯盟"
del info["stu1004"] # Python 內建的通用刪除方法,可以用來刪字典,也可以刪列表,任何物件
print(info)
---------------執行結果---------------
{'stu1002': 'Steve Rogers', 'stu1001': 'Tony Stark', 'stu1003': 'Bruce Banner'}
{'stu1002': 'Steve Rogers', 'stu1001': '東尼史塔克', 'stu1003': 'Bruce Banner'}
Process finished with exit code 0
Method 2:dic.pop()
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
#print(info["stu1001"])
info["stu1001"] = "東尼史塔克"
info["stu1004"] = "復仇者聯盟"
info.pop("stu1004") # 一定要指定一個key,不指定就會報錯
print(info)
---------------執行結果---------------
{'stu1001': 'Tony Stark', 'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers'}
{'stu1001': '東尼史塔克', 'stu1003': 'Bruce Banner', 'stu1002': 'Steve Rogers'}
Process finished with exit code 0
Method 3:dic.popitem()
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info)
#print(info["stu1001"])
info["stu1001"] = "東尼史塔克"
info["stu1004"] = "復仇者聯盟"
info.popitem() # 如果沒指定,就會隨機刪
print(info)
---------------執行結果---------------
{'stu1002': 'Steve Rogers', 'stu1003': 'Bruce Banner', 'stu1001': 'Tony Stark'}
{'stu1003': 'Bruce Banner', 'stu1001': '東尼史塔克', 'stu1004': '復仇者聯盟'}
Process finished with exit code 0
接下來,我們只想打印出,字典中所有的值
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info.values())
---------------執行結果---------------
dict_values(['Tony Stark', 'Steve Rogers', 'Bruce Banner'])
Process finished with exit code 0
看起來成功了,那既然可以只打印值,應該也可以只打印字典中所有的key
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info.keys())
---------------執行結果---------------
dict_keys(['stu1001', 'stu1002', 'stu1003'])
Process finished with exit code 0
唔,成功打印出所有的key了,再來我們來新增一個成員好了
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
info.setdefault('stu1007', "Phil Coulson")
print(info)
---------------執行結果---------------
{'stu1003': 'Bruce Banner', 'stu1001': 'Tony Stark', 'stu1007': 'Phil Coulson', 'stu1002': 'Steve Rogers'}
Process finished with exit code 0
唔,看起來也成功新增一個人員了,那假設如果用dict.setdefault('key', 'value')
這種語法,能不能拿來修改已存在的值,來試試唄
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
info.setdefault('stu1007', "Phil Coulson")
print(info)
info.setdefault('stu1003', "Nick Fury")
print(info)
---------------執行結果---------------
{'stu1002': 'Steve Rogers', 'stu1007': 'Phil Coulson', 'stu1003': 'Bruce Banner', 'stu1001': 'Tony Stark'}
{'stu1002': 'Steve Rogers', 'stu1007': 'Phil Coulson', 'stu1003': 'Bruce Banner', 'stu1001': 'Tony Stark'}
Process finished with exit code 0
嗯,看起來 stu1003
的值,並沒有被改變,所以dict.setdefault('key', 'value)
的主要功能就是把不存在於字典中的key,給建立起來
試試更新字典呢?
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
info2 = {
'stu1001': "Jarvis",
'stu2002': "Maria Hill",
}
info.update(info2)
print(info)
---------------執行結果---------------
{'stu1002': 'Steve Rogers', 'stu2002': 'Maria Hill', 'stu1001': 'Jarvis', 'stu1003': 'Bruce Banner'}
Process finished with exit code 0
觀察一下,發現當二個字典中,有二個一樣的key
時,如果使用了dict.update()
就會被更新了。
以上面代碼為例,這二個字典中,都有一個key
叫 stu1001
,但二個分別代表不同的值,info{'stu1001': "Tony Stark"}
,而 info2{'stu1001': "Jarvis"}
,當執行info.update(info2)
時,是把二個字典給合併
了,如果有對到一樣的key
就更新,沒有的話,就建立一組新的key-value,這就是dict.update()
的作用。
接下來試試dict.items()
,觀察一下,有什麼作用
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
print(info.items())
---------------執行結果---------------
dict_items([('stu1003', 'Bruce Banner'), ('stu1001', 'Tony Stark'), ('stu1002', 'Steve Rogers')])
Process finished with exit code 0
唔…看起來是把字典給轉成列表了。
接下來試一下怎麼做初始化字典
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
info2 = info.fromkeys([9, 8, 7])
print(info2)
---------------執行結果---------------
{8: None, 9: None, 7: None}
Process finished with exit code 0
咦,奇怪,為什麼不是用info.fromkeys([9, 8, 7])
嗎?怎麼打印出來的全都不一樣了,那是因為其實跟info
這個字典無關了,所以直接用dict.fromkeys(seq, value=none)
來驗証一下吧
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
info2 = dict.fromkeys([9, 8, 7], "test")
print(info2)
---------------執行結果---------------
{8: 'test', 9: 'test', 7: 'test'}
Process finished with exit code 0
這次就不透過info.fromkeys()
來調用了,直接使用dict.fromkeys()
,這樣就完成一個初始化字典啦,並且還直接賦值了。
再來觀察一下,下面這個代碼
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
info2 = dict.fromkeys([9, 8, 7], [1, {"name":"ironman"}, 9527])
print(info2)
info2[8][1]["name"] = "Bruce Lee"
print(info2)
---------------執行結果---------------
{8: [1, {'name': 'ironman'}, 9527], 9: [1, {'name': 'ironman'}, 9527], 7: [1, {'name': 'ironman'}, 9527]}
{8: [1, {'name': 'Bruce Lee'}, 9527], 9: [1, {'name': 'Bruce Lee'}, 9527], 7: [1, {'name': 'Bruce Lee'}, 9527]}
Process finished with exit code 0
有發現什麼嗎?我們原以為是初始化了三個獨立的數據,其實不是的,這個就跟之前講到的淺copy
有點類似,看下圖說明好了
dict.fromkeys() 較適用於一層式的字典,多層式的字典就不要用了
再來試一下,字典的循環是怎麼使用
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
for i in info:
print(i)
---------------執行結果---------------
stu1001
stu1003
stu1002
Process finished with exit code 0
咦,只有打印出key,如果也想把值給打印出來呢?
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
for i in info:
print(i, info[i])
---------------執行結果---------------
stu1001 Tony Stark
stu1003 Bruce Banner
stu1002 Steve Rogers
Process finished with exit code 0
還有另一種方法也可以同時打印出 key-value
的循環
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
info = {
'stu1001': "Tony Stark",
'stu1002': "Steve Rogers",
'stu1003': "Bruce Banner",
}
for k, v in info.items():
print(k, v)
---------------執行結果---------------
stu1003 Bruce Banner
stu1002 Steve Rogers
stu1001 Tony Stark
Process finished with exit code 0
那這二種有什麼差別呢?其實第一種的效率比較好,因為第一種是透過key的方式去取值
,但第二種多了一個把字典轉成列表的過程
,如果當數據量較大時,就不適合用第二種方式。
接下來,再寫稍稍複雜一點的,巢狀式(嵌套)(nested)字典
,並修改掉其中一個值
#!/usr/bin/env python3
# -*- coding:utf-8 -*-
shopping_online_catalog = {
"歐美": {
"www.amazon.com": ["美國最大購物網站", "亞馬遜"],
"www.ebay.com": ["美國知名購物網站", "eBay"],
"www.kickstarter.com": ["美國募資平台", "有很多有趣的專案在募資"]
},
"日本": {
"media.buyee.jp": ["日本代購網站", "不會日文也可以買,日本雅虎官方合作夥伴"],
"global.rakuten.com": ["日本樂天網站", "好像是日本第一大購物網站?"]
},
"大陸": {
"www.taobao.com": ["大陸淘寶網", "應該是大陸最大的購物網站吧?!"],
"www.jd.com": ["大陸京東商城", "其實我也不知道它在賣啥的"]
}
}
---------------執行結果---------------
{'大陸': {'www.taobao.com': ['大陸淘寶網', '應該是大陸最大的購物網站吧?!'], 'www.jd.com': ['大陸京東商城', '我只知道他們技術很牛逼']}, '日本': {'media.buyee.jp': ['日本代購網站', '不會日文也可以買,日本雅虎官方合作夥伴'], 'global.rakuten.com': ['日本樂天網站', '好像是日本第一大購物網站?']}, '歐美': {'www.amazon.com': ['美國最大購物網站', '亞馬遜'], 'www.kickstarter.com': ['美國募資平台', '有很多有趣的專案在募資'], 'www.ebay.com': ['美國知名購物網站', 'eBay']}}
Process finished with exit code 0
key
盡量不要使用中文字,很容易因為字符編碼不一致,而導致取不到值或是程序失敗
參考資料: