Python笔记005——列表

列表基础

列表定义：一有序数据集合用逗号间隔用方括号括起来

列表的索引访问（索引list_name[index]和切片list_name[start:end:step]）

1 wu=[1,2,3,4]
2 print(wu[1])
3 wu[1]=[5,6,7]
4 print(wu)
5 print(wu[1][1])

[[email protected] ~]# python 1.py
2
[1, [5, 6, 7], 3, 4]
6

列表遍历

 1 wu=[1,2,3,4]
 2 #### iteror
 3 for i in wu:
 4     print(i),
 5    #print(i,)
 6    #print(i)
 7 print(‘‘)
 8 i=0
 9 while i<len(wu):
10     print(wu[i]),
11     i +=1

[[email protected] ~]# python 1.py
1 2 3 4
1 2 3 4

理解for迭代

1 a=range(1,10)
2 for x in a:
3      print(‘for‘,x)
4      a.pop(1)
5      print(a)

[[email protected] ~]# python 1.py
(‘for‘, 1)
[1, 3, 4, 5, 6, 7, 8, 9]
(‘for‘, 3)
[1, 4, 5, 6, 7, 8, 9]
(‘for‘, 5)
[1, 5, 6, 7, 8, 9]
(‘for‘, 7)
[1, 6, 7, 8, 9]
(‘for‘, 9)
[1, 7, 8, 9]

列表里的最大值

 1 li=[23,45,55,66,743]
 2 i=1
 3 max=li[0]
 4 while i<len(li):
 5    if li[i]>max:
 6        max=li[i]
 7    i +=1
 8 print(‘max‘,max)
 9 print(‘###‘)
10 max=li[0]
11 for i in li:
12     if i>max:
13        max=i
14 print(‘max‘,max)

[[email protected] ~]# python 1.py
(‘max‘, 743)
###
(‘max‘, 743)

找第二大值

 1 li=[23,45,55,66,743]
 2 i=0
 3 max1=li[0]
 4 max2=li[0]
 5 while i<len(li):
 6     if max1<li[i]:
 7        max2=max1
 8        max1=li[i]
 9     else:
10         if max2<li[i]:
11            max2=li[i]
12     i +=1
13 print(‘max1‘,max1)
14 print(‘max2‘,max2)

[[email protected] ~]# python 1.py
(‘max1‘, 743)
(‘max2‘, 66)

方法二：

 1 li=[23,45,55,66,743]
 2 i=0
 3 max1=li[0]
 4 max2=li[0]
 5 for x in li:
 6     if max1<x:
 7        max2=max1
 8        max1=x
 9     else:
10         if max2<x:
11            max2=x
12 print(‘max1‘,max1)
13 print(‘max2‘,max2)

列表运算

列表加法

1 li1=[1,2,3]
2 li2=[4,5,6]
3 li=li1+li2
4 print(li)

[[email protected] ~]# python 1.py
[1, 2, 3, 4, 5, 6]

1 li1=range(1,10)
2 li2=range(11,20)
3 print(li1)
4 print(li2)
5 i=0
6 while i <len(li1):
7     li1[i] += li2[i]
8     i +=1
9 print(li1)

[[email protected] ~]# python 1.py
[1, 2, 3, 4, 5, 6, 7, 8, 9]
[11, 12, 13, 14, 15, 16, 17, 18, 19]
[12, 14, 16, 18, 20, 22, 24, 26, 28]

打印多层列表

index函数

1 li=range(1,11)
2 print(li)
3 print(li.index(6))

[[email protected] ~]# python 1.py
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
5

index函数

>>> li=range(1,11)
>>> li
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> li[3:9]
[4, 5, 6, 7, 8, 9]
>>> li[-7:-1]
[4, 5, 6, 7, 8, 9]
>>> li[li.index(4):li.index(9)+1]
[4, 5, 6, 7, 8, 9]

正负坐标的关系

>>> li=range(10,2100,2)
>>> li[li.index(120):li.index(160)+1]
[120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160]
>>> li[li.index(120)-len(li):li.index(160)+1-len(li)]
[120, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, 150, 152, 154, 156, 158, 160]

 li=range(1,11) 1 >>> li[3:8]
 2 [4, 5, 6, 7, 8]
 3 >>> li[-7:-2]
 4 [4, 5, 6, 7, 8]
 5 >>> li[3:8:1]
 6 [4, 5, 6, 7, 8]
 7 >>> li[-7:-2:1]
 8 [4, 5, 6, 7, 8]
 9 >>> li[li.index(4):li.index(8)+1]
10 [4, 5, 6, 7, 8]
11 >>> li[li.index(8):li.index(4)-1:-1]
12 [8, 7, 6, 5, 4]
13 >>> li[:]
14 [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
15 >>> li[::-1]
16 [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]