6-18-00:18 day 12 list-1:00

Posted 2020-11-19 yikedashuyikexiaocao

list

 []中括号括起来，逗号，分割每个元素，列表元素可以是数字，字符串，列表，布尔值

所以都能放进去

索引，切片

 

test=["ds","df",433,["dfsdf"],"ds"]
del test[1]# 删除

print(test)
test[0]=[12,4,5,5]#修改
print(test)//[‘ds‘, 433, [‘dfsdf‘], ‘ds‘]，[[12, 4, 5, 5], 433, [‘dfsdf‘], ‘ds‘]

数字无法for循环
字符串转换列表，内部使用for循环

test=["ds","df","433","dfsdf","ds"]

v=" ".join(test)#只有字符串join ，有数字无法for循环

print(v)//ds df 433 dfsdf ds

s=" "
for i in test:
    s+=str(i)
print(s)//dsdf433dfsdfds

test=["ds","df",433,"dfsdf","ds"]
test.append(12)#在追加元素
print(test)//[‘ds‘, ‘df‘, 433, ‘dfsdf‘, ‘ds‘, 12]

 2 清空列表
# li.clear()
# print(li)

# 3 拷贝，浅拷贝
# v = li.copy()
# print(v)
# 4. 计算元素出现的次数
# v = li.count(22)
# print(v)

# 5. 扩展原列表，参数：可迭代对象
# li = [11, 22, 33, 22, 44]
# li.append([9898,"不得了"])
# [11, 22, 33, 22, 44, [9898, ‘不得了‘]]

# li.extend([9898,"不得了"])
# for i in [9898,"不得了"]:
#     li.append(i)
# [11, 22, 33, 22, 44, 9898, ‘不得了‘]

# 6. 根据值获取当前值索引位置（左边优先）
# li = [11, 22, 33, 22, 44]
# v= li.index(22)
# print(v)1

# 7. 在指定索引位置插入元素
# li = [11, 22, 33, 22, 44]
# li.insert(0,99)
# print(li)[99,..]

 删除某个值(1.指定索引；2. 默认最后一个)，并获取删除的值

test=["ds","df",433,"dfsdf","ds"]
v=test.pop()
print(test)
print(v)

9. 删除列表中的指定值，左边优先
# li = [11, 22, 33, 22, 44]
# li.remove(22)
# print(li)
# PS: pop remove del li[0]  

# 将当前列表进行翻转
li = [11, 22, 33, 22, 44]
li.reverse()
print(li)//[44, 22, 33, 22, 11]

# 11 列表的排序
# li = [11,44, 22, 33, 22]
# li.sort()//[11, 22, 22, 33, 44]

li.sort(reverse=True)
print(li)//[44, 33, 22, 22, 11]

# 补充：字符串创建后，不可修改

# 列表，有序；元素可以被修改