4、列表

1.1 列表的介绍
列表是python的基础数据类型之⼀一 ,其他编程语⾔言也有类似的数据类型. 比如JS中的熟组, java中的数组等. 它是以[ ]括起来, 每个元素⽤用' , '隔开⽽而且可以存放各种数据类型:

lst = [1, '哈哈', "吼吼", [1,8,0,"百度"], ("我","叫", "元", "组"), "abc", {"我叫":"dict字典"},{"我叫集合","集合"}]

列表相比于字符串串. 不仅可以存放不同的数据类型. ⽽而且可以存放⼤大量量的数据. 32位python可以存放: 536870912个元素, 64位可以存放: 1152921504606846975个元素.而且列表是有序的(按照你保存的顺序),有索引, 可以切片方便取值.
2.2 列表的索引和切片

列表和字符串串一样也拥有索引:

list = ['哈哈','呵呵','嘻嘻','哼哼']
list[0] ="GG"
print(list)
list[1] = "HH"
print(list)

列表的切片:

list = ['哈哈','呵呵','嘻嘻','哼哼']
print(list[0:3])   # ['哈哈', '呵呵', '嘻嘻']
print(list[:3])    # ['哈哈', '呵呵', '嘻嘻']
print(list[1::2])  # ['呵呵', '哼哼']
print(list[2::-1]) # ['嘻嘻', '呵呵', '哈哈']
print(list[-1:-3:-2]) # ['哼哼']

二. 列表的增删改查

1. 增, 注意, list和str是不一样的. lst可以发生改变. 所以直接就在原来的对象上进⾏了操作

list = ['哈哈','呵呵','嘻嘻','哼哼']
print(list)
list.append("嘎嘎")
print(list)

list = []
while True:
    content = input("请输入你要录入的员工信息，输入Q退出:")
    if content.upper() =="Q":
        break
    list.append(content)
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼']
list.insert(1,"嘎嘎") #在1的位置插入嘎嘎，原来元素向后移动一位
print(list)

# 迭代添加

list = ['哈哈','呵呵','嘻嘻','哼哼']
list1 = ["星星","月亮"]
list.extend(list1)
print(list)

2. 删除

pop, remove, clear, del

list = ['哈哈','呵呵','嘻嘻','哼哼']
print(list)
deleted = list.pop()    # 删除最后一个
print("被删除的", deleted)
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼']
deleted = list.pop(1)          # 删除1号元素
print("被删除的", deleted)
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼']
deleted = list.remove("嘻嘻")  # 删除指定元素
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼']
deleted = list.clear()  # 清空list
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼']
del list[1:3]
print(list)

3. 修改
索引切片修改

list = ['哈哈','呵呵','嘻嘻','哼哼']
list[1]="GG"
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼']
list[:3:2]=["G","T"]
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼']
list[1:3]=["gg"]
print(list)

4. 查询, 列表是一个可迭代对象, 所以可以进行for循环

list = ['哈哈','呵呵','嘻嘻','哼哼']
for c in list:
    print(c)

5、其他操作

list = ['哈哈','呵呵','嘻嘻','哼哼',"哈哈","哈哈"]
print(list.count("哈哈"))

list = [1,11,22,2]
list.sort()
print(list)    #排序，默认升序
list.sort(reverse=True)  # 降序
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼',"哈哈","哈哈"]
print(list)
list.reverse()
print(list)

list = ['哈哈','呵呵','嘻嘻','哼哼',"哈哈","哈哈"]
print(len(list))   #列表的长度

三. 列表的嵌套
采用降维操作.一层一层的看就好.

list= [1,"xx","zz",["GG",["KK"],"LL"]]
print(list[2])      #找到zz
print(list[3][1][0])  #找到KK
print（list[1][1]）    #找到x

# 将zz拿到 然后首字母大写 再放回去
list= [1,"xx","zz",["GG",["KK"],"LL"]]
s = list[2]
s = s.capitalize()
list[2] = s
print(list)

#把zt变成zx
list= [1,"xx","zt",["GG",["KK"],"LL"]]
list[2]=list[2].replace("t","x")
print(list)

# 把GG换成GT
list= [1,"xx","zt",["GG",["KK"],"LL"]]
list[3][0] = list[3][0].replace("GG","GT")
print(list)

#在KK后面增加PP
list= [1,"xx","zt",["GG",["KK"],"LL"]]
list[3][1].append("PP")
print(list)

四. 元组和元组嵌套
元组: 俗称不可变的列表.又被成为只读列表, 元组也是python的基本数据类型之一, ⽤用小括号括起来, 里面可以放任何数据类型的数据, 查询可以. 循环也可以. 切片也可以. 但就是不能改.

tu = (1, "太白", "李白", "太黑", "怎么黑")
print(tu)
print(tu[0])
print(tu[2])
print(tu[2:4])  # 切⽚片之后还是元组

# for循环遍历元组
for el in tu :
    print(el)

tu = (1,"哈哈",[],"呵呵")
# tu[2] = ["abcd"]   #这样改不行
tu[2].append("马化腾")  #可以改
tu[2].append("王健林")
print(tu)

关于不可变, 注意: 这里元组的不可变的意思是子元素不可变. 而⼦元素内部的子元素是可以变, 这取决于子元素是否是可变对象.
元组中如果只有一个元素. ⼀定要添加一个逗号, 否则就不是元组

tu = (1,)
print(type(tu))

元组也有count(), index(), len()等⽅法.

tu = ("a","b","c","d","a")
print(tu.count("a"))

tu = ("a","b","c","d","a")
print(tu.index("b"))

tu = ("a","b","c","d","a")
print(len(tu))

五. range
range可以帮我们获取到一组数据. 通过for循环能够获取到这些数据.

for num in range(10):
    print(num)
for num in range(1,10,2):
    print(num)
for num in range(10,1,-1):
    print(num)    # 反着来, 和切片一样