4.Python的不堪一擊到初學乍練(列表,元組)

Python(列表,元組)

一.列表

1. 列表初識

   • 列表是python的基礎數據類型之一,其餘編程語言也有相似的數據類型.
     好比JS中的數組, java中的數組等等,它是以[ ]括起來, 每一個元素用","隔開而且能夠存放各類數據類型.
   • 列表相比於字符串,不只能夠存放不一樣的數據類型,而且能夠存放大量的數據.
     當32位Python能夠存放:536870912個元素, 當64位Python能夠存放:1152921504606846975個元素,而且列表是按照你保存的順序進行排序的,有索引而且能夠切片,方便取值.

2. 列表索引,切片和操做

   1.1 列表的索引

   ​ 列表與字符串同樣也有索引:

   # 列表索引的應用
   lst = ["asd", "你好", "hell world", 123, "昇仙"]
   print(lst[0]) # 獲取第一個元素
   print(lst[1]) # 獲取第二個元素
   print(lst[2]) # 獲取第三個元素
   print(lst[3]) # 獲取第四個元素
   print(lst[4]) # 獲取第五個元素
   # 列表是可變的與字符串不一樣這點要注意,在列表的操做中會有說明.

   1.2 列表的切片

   ​ 列表與字符串同樣可進行切片操做

   lst = ["asd","你好","hell world",123,"昇仙"]
   print(lst[0:3]) # ["asd","你好","hell world"]
   print(lst[:3]) # ["asd","你好","hell world"]
   print(lst[1::2]) # ["你好",123] 列表一樣有步長
   print(lst[2::-1]) # ["hell world","你好","asd"] 步長位置的正負控制着取值的方向
   print(lst[-1:-4:-2]) # ["昇仙","hell world"]
   # 列表和字符串的操做基本相似,所以操做起來並不難觸類旁通便可.

   1.3 列表的操做(增,刪,改,查,其餘操做)

   注意 : list和str不同, lst能夠發生改變.,因此能夠直接在原來list對象上進行操做.

   ​ 1.3.1 列表的增長

   # 在列表後新增
   lst = ["asd","你好","hell world",123,"昇仙"]
   print(lst)
   lst.append("wusir")
   print(lst) # ["asd","你好","hell world",123,"昇仙","wusir"]
   ---------------------------------
   # 根據索引位置插入
   lst = ["asd","你好","hell world",123,"昇仙"]
   lst.insert(1,"成仙") # 在索引爲1的位置插入劉德華,原來的元素向後移動一位.
   print(lst) # ["asd","成仙","你好","hell world",123,"昇仙"]
   ---------------------------------
   # 迭代添加
   lst = ["asd","你好","hell world",123,"昇仙"]
   lst2 = ["昇仙成功","昇仙失敗"]
   lst.extend(lst2)
   print(lst) # ["asd","你好","hell world",123,"昇仙","昇仙成功","昇仙失敗"]
   print(lst2) # ["昇仙成功","昇仙失敗"]
   # lst2列表添加到lst列表中,lst2自己不變.

   ​ 1.3.2 列表的刪除

   ​ 列表的刪除有四種方式(pop,remove,clear,del)

   # pop刪除用法
   lst = ["asd","你好","hell world",123,"昇仙"]
   print(lst)
   el = lst.pop() # 當pop()括號內爲空時,默認刪除最後一個索引所對應的的數據.
   print(el) # 打印結果:昇仙,pop刪除列表的某一項時,會有返回值,其返回值就是被pop刪除的內容.
   print(lst) # ["asd","你好","hell world",123]
   
   lst = ["asd","你好","hell world",123,"昇仙"]
   el2 = lst.pop(2) # 刪除索引爲2的位置的值
   print(el2) # hell world
   print(lst) # ["asd","你好",123,"昇仙"]
   ---------------------------------
   # remove刪除用法
   lst = ["asd","你好","hell world",123,"昇仙"]
   lst.remove("昇仙") # 能夠刪除指定元素,當刪除不存在的元素會報錯
   print(lst) # ["asd","你好","hell world",123]
   ---------------------------------
   # clear刪除用法
   lst.clear() # 清空list
   print(lst) # []
   ---------------------------------
   # 切片刪除
   del lst[1:3] # 強制刪除
   print(lst) # ["asd",123,"昇仙"]

   ​ 1.3.3 列表的修改

   # 列表的修改
   lst = ["asd","你好","hell world",123,"昇仙"]
   lst[1] = "飛昇" # 把1號元素修改爲飛昇
   print(lst) # ["asd","飛昇","hell world",123,"昇仙"]
   lst[:4:2] = ["返璞歸真", "融會貫通"] # 切片修改也能夠,同時注意當步長不是1時,元素的個數要一一對應額不然會報錯
   print(lst) # ["返璞歸真","飛昇","融會貫通",123,"昇仙"]
   lst[1:4] = ["霸氣外露"] # 若是切片沒有步長或者步長是1時,則不用管替換的個數.
   print(lst) # ["返璞歸真","霸氣外露","昇仙"]

   ​ 1.3.4 列表的查詢

   ​ 列表是一個能夠迭代的對象

   # 用for查詢打印列表每個元素
   lst = ["asd","你好","hell world",123,"昇仙"]
   for el in lst:
    print(el)
   ---------------------------------
   # 查詢元素在列表中出現的次數
   lst = ["asd","你好","hell world",123,"昇仙"]
   c = lst.count("昇仙") # 查詢昇仙出現的次數
   print(c) # 1
   ---------------------------------
   # 查詢列表的長度
   lst = ["asd","你好","hell world",123,"昇仙"]
   l=len(lst) # 列表的長度,與字符串的使用方式相同
   print(l) # 5

   ​ 1.3.4 列表的其餘操做

   # 升序
   lst = [1,2,15,23,4,33]
   lst.sort() # 排序,默認爲升序.
   print(lst) # [1,2,4,15,23,33]
   ---------------------------------
   # 降序
   lst.sort(reverse=True) # 降序
   print(lst) # [33,23,15,4,2,1]
   ---------------------------------
   # 翻轉(倒序)
   lst = ["asd","你好","hell world",123,"昇仙"]
   lst.reverse() # 此方法只針對列表內的各個元素,倒序
   print(lst) # ["昇仙",123,"hell world","你好","asd"]

3. 列表嵌套

   一層一層看靈活運用便可,融會貫通.

   lst = ["武當","峨眉","少林",["崆峒",["極樂谷"],"華山"],"魔教"]
   # 找到峨眉
   print(lst[2])
   # 找到少林和魔教
   print(lst[2:])
   # 找到崆峒
   print(lst[3][0])
   # 將崆峒改爲丐幫
   lst[3][0]="丐幫"
   print(lst) # ['武當','峨眉','少林',['丐幫',['極樂谷'],'華山'],'魔教']
   # 在lst列表後添加"丐幫"
   lst.append("丐幫")
   print(lst) # ['武當','峨眉','少林',['崆峒',['極樂谷'],'華山'],'魔教','丐幫']

二.元組

1. 元組初識

   ​ 元組俗稱不可變的列表,又稱爲只讀列表,元組也是python的基本數據類型之一,用小括號括起來,裏面能夠聽任何數據類型的數據,循環也能夠,查詢能夠,切片也能夠,就是不能改.

   ​ 注意: 這裏元組的不可變的意思是當子元素是不可變對象時元素不可變,當子元素爲可變對象時是能夠變的, 這取決於子元素是不是爲可變對象.

   ​ 元組中若是隻有一個元素,須要添加一個逗號,不然就不是一個元組,當tu=()時,print(type(tu)),打印結果顯示tu是元組.

2. 元組嵌套

   ​ 元組也有,len(),count(),index()等方法,能夠本身嘗試直至融會貫通.

   # 元組取值和切片
   tup = ("asd","你好","hell world",123,"昇仙")
   print(tup[0]) # asd
   print(tup[2]) # hell world
   print(tup[2:]) # ("hell world",123,"昇仙") 切片後仍然是元組
   ---------------------------------
   # for循環
   tup = ("asd","你好","hell world",123,"昇仙")
   for el in tup:
    print(el)
   ---------------------------------
   # 當元組內的子元素時可變類型時能夠進行操做,將武當換成丐幫
   tup = ("asd","你好","hell world",123,["武當","峨眉","少林"])
   tup[-1][0]="丐幫"
   print(tup) # ("asd","你好","hell world",123,["丐幫","峨眉","少林"])
   # 這裏元組的不可變的意思是子元素不可變,而字元素內部的子元素是能夠變, 這取決於子元素是不是可變對象.