Python 入門系列 —— 21. dict 的介紹

Dictionary

字典經常使用於存儲鍵值對的集合,它是一種無序,可修改而且不容許重複,字典是用 {} 來表示,並帶有 k/v 鍵值對,好比下面定義的字典結構。python

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print(thisdict)


PS E:\dream\markdown\python> & "C:/Program Files (x86)/Python/python.exe" e:/dream/markdown/python/app/app.py
{'brand': 'Ford', 'model': 'Mustang', 'year': 1964}

字典項

字典中的項是以 key-value 形式展先的,一般咱們用 key 來獲取字典中的內容,以下代碼所示:markdown

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print(thisdict["brand"])

PS E:\dream\markdown\python> & "C:/Program Files (x86)/Python/python.exe" e:/dream/markdown/python/app/app.py
Ford

無序,可修改

當咱們說字典是無序的,意味着它並無一個預先定義好的順序,也就不能經過 index 的方式去獲取 dictionary 中的 item。app

字典是可修改的,意味着咱們能夠在已建立的字典中修改,新增,刪除項。this

不容許重複

不容許重複,意味着同一個key 不可能有兩個 item,有些朋友可能就要問了,若是在新增時遇到重複的 key 怎麼辦呢? python 中會默認覆蓋掉以前同名key,以下代碼所示:code

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964,
  "year": 2020
}
print(thisdict)

PS E:\dream\markdown\python> & "C:/Program Files (x86)/Python/python.exe" e:/dream/markdown/python/app/app.py
{'brand': 'Ford', 'model': 'Mustang', 'year': 2020}

字典長度

要想判斷字典中有多少個 item,能夠使用 len() 方法便可,好比下面的代碼:get

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964,
  "year": 2020
}

print(len(thisdict))

PS E:\dream\markdown\python> & "C:/Program Files (x86)/Python/python.exe" e:/dream/markdown/python/app/app.py
3

字典項的數據類型

字典項的value值能夠是任何類型,好比 int,string,array 等,以下代碼所示:string

thisdict = {
  "brand": "Ford",
  "electric": False,
  "year": 1964,
  "colors": ["red", "white", "blue"]
}

type()

本質上來講,dict 就是一個名爲 dict 的 class 類,以下代碼所示:it

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}
print(type(thisdict))

PS E:\dream\markdown\python> & "C:/Program Files (x86)/Python/python.exe" e:/dream/markdown/python/app/app.py
<class 'dict'>
譯文連接: https://www.w3schools.com/pyt...
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