python学习-17 列表list 2

# 1. 选择嵌套列表里的元素（内部进行了for循环）

li = [1,2,"age",["熊红","你好",["",45]],"abc",True]
a = li[3][2][1]
print(a)

运行结果：

45

Process finished with exit code 0

#2. 字符串转换列表

a = "iamchinese"
b =list(a)
print(b)

运行结果：

['i', 'a', 'm', 'c', 'h', 'i', 'n', 'e', 's', 'e']

Process finished with exit code 0

#3. 列表转换字符串

第一种方法：（for循环）

li =[123,456,"abcdefg"]
b = " "
for a in li:
   b=b+str(a)
print(b)

运算结果：

123456abcdefg

Process finished with exit code 0

第二种方法：（列表中的元素只有字符串时）

li =["abcdefg"]
a ="".join(li)
print(a)

运行结果：

abcdefg

Process finished with exit code 0

#4. list 的其他功能

-追加（也可以加字符串，列表等）

li = [123,13121,55]
li.append(6)
print(li)

运算结果：

[123, 13121, 55, 6]

Process finished with exit code 0

-清空

li = [123,13121,55]
li.clear()
print(li)

运算结果：

[]

Process finished with exit code 0

-浅拷贝

li = [123,13121,55]
a = li.copy()
print(li)
print(a)

运算结果：

[123, 13121, 55]
[123, 13121, 55]

Process finished with exit code 0

-计数

li = [55,123,13121,55]
a =li.count(55)         #计算 55 出现过几次

print(a)

运算结果：

2

Process finished with exit code 0

-迭加

li = [1,2,3,4,5]
li.extend([7,8,9,"你好"])

print(li)

运算结果：

[1, 2, 3, 4, 5, 7, 8, 9, '你好']

Process finished with exit code 0

ps: append 将整个元素添加， extend 是内部经过for循环将一个添加

-获取位置

li = [1,22,33,4,5,33]
a=li.index(33)      #（从左向右获取索引位置（获取到第一个就不会继续了），可以指定位置li.index(0:3)）

print(a)

运算结果：

2           #(索引，不是数量)

Process finished with exit code 0

-删除某个元素并获取删除的元素

li = [1,22,33,4,5,33]
a=li.pop()             #  可以指定索引位置（不指定索引，默认删除最后一个）
print(li)
print(a)

运算结果：

[1, 22, 33, 4, 5]
33

Process finished with exit code 0

-删除指定元素

li = [1,22,33,4,5,33]
li.remove(33)    #从左向右只删除第一个
print(li)

运算结果：

[1, 22, 4, 5, 33]

Process finished with exit code 0

-反转

li = [1,22,33,4,5,33]
li.reverse()
print(li)

运算结果：

[33, 5, 4, 33, 22, 1]

Process finished with exit code 0

-排序

li = [1,22,33,4,5,33]
li.sort(reverse=True)        # 括号里不填默认从小到大排序
print(li)

运算结果：

[33, 33, 22, 5, 4, 1]

Process finished with exit code 0