python基础之列表list

Posted 2022-08-08 meifei

list常用命令：
索引/切片：list[index] list[start_index:end_index]
增：list.append(obj) list.insert(index,obj) list.extend(obj)
删：list.pop(index) list.pop() list.remove(obj) list.clear() del list  del list[start_inde:end_index]
改：list[index] = obj list[start_index:end_indes] = obj
查：for i in list:   list[index] list[start_index:end_indes]
统计: len(list) list.count(obj) list.index(obj)
排序：list.sort()  list.sort(reverse=True) list.reverse()
嵌套查询：list[index][index]

1，切片：同str顾头不顾尾
li[0],li[0:3]
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1[3]
print(l2)

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l1 = [1,2,3,[3,2,4],4]
l2 = l1[0:3]
print(l2)

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2，增加：无返回值
追加：li.append(‘e‘)
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.append([7,8,9])
print(l1)

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l1 = [1,2,3,[3,2,4],4]
l2 = l1.append(‘eee‘)
print(l1)

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插入：li.insert(4,‘e‘)--在索引为4处插入e
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.insert(2,‘tt‘)
print(l1)

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分解追加元素：li.extend(‘[1,2,3]‘)--在li尾部追加1，2，3三个元素
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.extend([‘a‘,‘b‘])
print(l1)

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3，删除：返回删除的值
li.pop(2)--2表示索引删除
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.pop(1)
print(l1)

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li.pop()--默认删除最后一个元素
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.pop()
print(l1)

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li.remove(‘e‘)--e表示按元素删除
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.remove(3)
print(l1)

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li.clear()--清除列表
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.clear()
print(l1)

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del li--完全删除列表
ey:

l1 = [1,2,3,[3,2,4],4]
del l1
print(l1)

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del li[0:2]--切片删除列表
ey:

l1 = [1,2,3,[3,2,4],4]
del l1[0:2]
print(l1)

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4，更改值：
li[0] = ‘e‘ --按索引赋值更改值
ey:

l1 = [1,2,3,[3,2,4],4]
l1[1] = ‘e‘
print(l1)

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li[0:2] = ‘ssse‘--按切片赋值更改，元素分解增加值
ey:

l1 = [1,2,3,[3,2,4],4]
l1[1:2] = ‘eaas‘
print(l1)

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result:[1, ‘e‘, ‘a‘, ‘a‘, ‘s‘, 3, [3, 2, 4], 4]
 li[0:2] = [1,2,‘eee‘] --列表插入
ey:

l1 = [1,2,3,[3,2,4],4]
l1[0:2] = [‘a‘,2,‘b‘]
print(l1)

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result:[‘a‘, 2, ‘b‘, 3, [3, 2, 4], 4]
5，查询：
for 循环查找：for i in li:
ey:

l1 = [1,2,3,[3,2,4],4]
for li in l1:
    print(li)

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切片查找：li[0:2]
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1[0]
print(l2)

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result:1
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1[0:3]
print(l2)

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result:[1, 2, 3]
6，公共方法：
长度：len(li)
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = len(l1)
print(l2)

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result:5
计数：li.count(‘e‘)--返回e个数
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.count(3)
print(l2)

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result:1
索引：li.index(‘e‘)--返回e的索引，如果e不存在报错
ey:

l1 = [1,2,3,[3,2,4],4]
l2 = l1.index(3)
print(l2)

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result:2
7，排序：
数字从小到大排序-正序：li.sort()
ey:

l1 = [1,2,3,5,4]
l2 = l1.sort()
print(l1)

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result:[1, 2, 3, 4, 5]
数字倒序：li.sort(reverse=true)
ey:

l1 = [1,2,3,5,4]
l2 = l1.sort(reverse=True)
print(l1)

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result:[5, 4, 3, 2, 1]
反转：li.reverse()
ey:

l1 = [1,2,-3,-5,4]
l2 = l1.reverse()
print(l1)

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result:[4, -5, -3, 2, 1]
8，列表嵌套：
li[1][1]---找到列表li第2个元素为str，找到str第二个元素
ey:

l1 = [1,2,-3,[7,8,9,‘e‘],4]
l2 = l1[3][3]
print(l2)

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result:e