Python 字典

列表

數據類型的分類

可變(不可哈希)的：list dict set
不可變(可哈希)的：str bool int tuple

1. 列表的建立

方法一：

l1 = [1,2,"哈哈哈"]

方法二：

li = list()

方法三：列表推導式

2. 增

• append
• insert
• extend

li = ["520","Python",123]
li.append("Faye")
print(li.append("append方法增長")) #不能打印它，結果是None
print(li)
li.insert(1,"哈哈哈") #按索引插入，把「哈哈哈」插入到索引爲1的位置
print(li)
li.extend("ABC123") #extend是迭代增長
print(li)

None
['520', 'Python', 123, 'Faye', 'append方法增長']
['520', '哈哈哈', 'Python', 123, 'Faye', 'append方法增長']
['520', '哈哈哈', 'Python', 123, 'Faye', 'append方法增長', 'A', 'B', 'C', '1', '2', '3']

要特別注意extend和append的區別！

li = ["蘋果","香蕉","菠蘿"]
li.extend(["番茄","青菜"])
print(li)
li.append(["中國","上海"])
print(li)

['蘋果', '香蕉', '菠蘿', '番茄', '青菜']
['蘋果', '香蕉', '菠蘿', '番茄', '青菜', ['中國', '上海']]

3.刪

• pop() 返回刪除的元素，再刪
• remove() 指定元素刪除，若是有多個元素，刪除（從左到右數的）第一個
• clear() 清空，變成一個空列表了，可是列表還在
• del() 能夠刪除內容也能夠刪除整個列表

#pop()
li = ["蘋果","香蕉","菠蘿","火龍果","西瓜","柿子"]
print(li.pop()) #默認刪除最後一個元素
print(li.pop(2)) #按索引刪
print(li)

柿子
菠蘿
['蘋果', '香蕉', '火龍果', '西瓜']

#remove()
li = ["蘋果","香蕉","蘋果","西瓜"]
li.remove("蘋果")
print(li)

['香蕉', '蘋果', '西瓜']

#clear
li = ["蘋果","香蕉","蘋果","西瓜"]
li.clear()
print(li)

[]

#del
li = ["蘋果","香蕉","菠蘿","蘋果","西瓜","水蜜桃","橘子"]
del li[3] #按索引刪
print(li) 
del li[::3] #按切片刪
print(li)
del li #把這個li刪了。print(li)會報錯

['蘋果', '香蕉', '菠蘿', '西瓜', '水蜜桃', '橘子']
['香蕉', '菠蘿', '水蜜桃', '橘子']

4.改

• 直接改
• 切片改

#直接改
li = ["蘋果","香蕉","水蜜桃","橘子"]
li[-2] = "hhhh"
print(li)

['蘋果', '香蕉', 'hhhh', '橘子']

#切片改
li = ["蘋果","香蕉","菠蘿","蘋果","西瓜","水蜜桃","橘子"]
li[2:] = "hh"
print(li)

['蘋果', '香蕉', 'h', 'h']

若是要變成 li = ["蘋果","香蕉","hh"] 怎麼辦呢？

#方法一：
li = ["蘋果","香蕉","菠蘿","蘋果","西瓜","水蜜桃","橘子"]
del li[2:]
li.append("hh")
print(li)

#方法二
li = ["蘋果","香蕉","菠蘿","蘋果","西瓜","水蜜桃","橘子"]
li[2:]=['hh']

5.查

• 按索引
• 按切片

li = ["蘋果","香蕉","菠蘿","蘋果","西瓜","水蜜桃","橘子"]
print(li[-3])
print(li[::2])

西瓜
['蘋果', '菠蘿', '西瓜', '橘子']