列表学习细节

 

names=['a','b','c']

numbers=[1,2,3]

kongs=[]

kong2=list()

print(names,numbers,kongs,kong2)

一般都用names=['a','b','c'] 和 names=[] 两种形式

names=['a','b',1,-1]
names[0]
'a'
names[-1]
-1

通过索引或下标取值，从0开始，倒数第一个就是-1

列表是可以重复的！

l01=['1','123','sdfa',0,1,2,33333,444,2,32,2,2,2,2,2,5,-6,-9,'gg']

print(l01)

查找

 

可见，找到的是第一个符合的下标

没有的元素会报错：

l01[l01.index(444)]
444

计数：
l01.count(2)
7

l01里有7个2

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切片

取其中一部分

 

l01[0:3]
['1', '123', 'sdfa']

顾头不顾尾，光标所在的段是截取的值

我想取444到-6的段

 

l01=['1','123','sdfa',0,1,2,33333,444,2,32,2,2,2,2,2,5,-6,-9,'gg']
print(l01)
idx1=l01.index(444)
idx2=l01.index(-6)
print(idx1,idx2)
g1=l01[idx1:idx2+1]
print(g1)

['1', '123', 'sdfa', 0, 1, 2, 33333, 444, 2, 32, 2, 2, 2, 2, 2, 5, -6, -9, 'gg']
7 16
[444, 2, 32, 2, 2, 2, 2, 2, 5, -6]

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取最后5个
g2=l01[-5:]
print(g2)
[2, 5, -6, -9, 'gg']

去前3个
g3=l01[:3]
print(g3)

取全部
print(l01[:])

从第2个到倒数第3个，每3个一取，3是步长
print(l01[1:-2:3])

print(l01[::2])

————————————————

n1=[1,2,3,'a','b','c','d']
n1.append('e')
print(n1)
[1, 2, 3, 'a', 'b', 'c', 'd', 'e']

n1.insert(0,0)
n1
[0, 1, 2, 3, 'a', 'b', 'c', 'd', 'e']

n1.insert(3,2.5)
n1
[0, 1, 2, 2.5, 3, 'a', 'b', 'c', 'd', 'e']

在c前插入B2C
n1.insert(n1.index('c'),'b2c')
n1
[0, 1, 2, 2.5, 3, 'a', 'b', 'b2c', 'c', 'd', 'e']

在a后插入‘a-b’
n1.insert(n1.index('a')+1,'a-b')
n1
[0, 1, 2, 2.5, 3, 'a', 'a-b', 'b', 'b2c', 'c', 'd', 'e']

修改就是直接赋值
n1[n1.index('c')]='c2c'
n1
[0, 1, 2, 2.5, 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd', 'e']

多值修改，少用
n1
[0, 1, 2, 2.5, 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd', 'e']
n1[2:4]='xyz uvw'
n1
[0, 1, 'x', 'y', 'z', ' ', 'u', 'v', 'w', 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd', 'e']

注意，不是替换成一个，而是拆分成单个字母，挤入，空格也算。

————————————————————————

n1
[0, 1, 'x', 'y', 'z', ' ', 'u', 'v', 'w', 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd', 'e']
n1.pop()
'e'
n1
[0, 1, 'x', 'y', 'z', ' ', 'u', 'v', 'w', 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd']

pop弹出，删除最后一个

删除第一个x元素
n1.remove('x')
n1
[0, 1, 'y', 'z', ' ', 'u', 'v', 'w', 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd']

del全局删除，不只是删列表，删的是下标
del n1[2]
n1
[0, 1, 'z', ' ', 'u', 'v', 'w', 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd']

del想删什么就删什么
del names
names
Traceback (most recent call last):
File "<input>", line 1, in <module>
NameError: name 'names' is not defined

批量删除
n1
[0, 1, 'z', ' ', 'u', 'v', 'w', 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd']
del n1[2:5]
n1
[0, 1, 'v', 'w', 3, 'a', 'a-b', 'b', 'b2c', 'c2c', 'd']

循环打印列表元素
n1=[1,2,3,'a','b','c','d']

for i in n1:
print(i)

 

n3=range(10)
n3
range(0, 10)
for i in n3:
print(i)

0
1
2
3
4
5
6
7
8
9

range（10）就是生成0-9的列表

for i in range(10):
print('row ',i)

for和while的区别：
for是有边界的，while可以是死循环

n1=[9,-2,42,7,'99','jack','E',0]
n1
[9, -2, 42, 7, '99', 'jack', 'E', 0]
列表是有序的，因为它是有索引下标的。

n1.sort()
Traceback (most recent call last):
File "<input>", line 1, in <module>
TypeError: '<' not supported between instances of 'str' and 'int'

print(n1)
n1.sort()
print(n1)

['99', 'TT', 'a', 'jack', 'E', 'T']
['99', 'E', 'T', 'TT', 'a', 'jack']

是按照编码顺序排序的

n1.reverse()
print(n1)
['99', 'E', 'T', 'TT', 'a', 'jack']
['jack', 'a', 'TT', 'T', 'E', '99']

反转

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列表拼接
n1=[1,2,3]
n2=['a','b','c']
n1+n2
[1, 2, 3, 'a', 'b', 'c']
n2.extend(n1)
n2
['a', 'b', 'c', 1, 2, 3]
n1
[1, 2, 3]

清空
n1.clear()
print(n1)

n1=[1,2,3]
n2=n1
n2
[1, 2, 3]
n1[1]='two'
n1
[1, 'two', 3]
n2
[1, 'two', 3]

列表赋值，是会指向同一个列表的。

n1
[1, 'two', 3]
n3=n1.copy()
n3
[1, 'two', 3]
n1[1]
'two'
n1[1]='second'
n1
[1, 'second', 3]
n3
[1, 'two', 3]

用了copy方法，则n1和n3是独立的，不影响。

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# coding:utf-8

# 1.创建一个空列表，命名为names,往里面添加old_driver,rain,jack,shanshan,peiqi,black_girl 元素
names=[]
names.append('old_driver')
names.append('rain')
names.append('jack')
names.append('shanshan')
names.append('peiqi')
names.append('black_girl')
print(names)

# 2.往names列表里black_girl前面插入一个alex
names.insert(names.index('black_girl'),'alex')
print(names)

# 3.把shanshan的名字改成中文，姗姗
names[names.index('shanshan')]='姗姗'
print(names)

# 4.往names列表里rain的后面插入一个子列表，[oldboy, oldgirl]
names.insert(names.index('rain')+1,['oldboy','oldgirl'])
print(names)

# 5.返回peiqi的索引值
print(names.index('peiqi'))

# 6.创建新列表[1,2,3,4,2,5,6,2],合并入names列表
n1=[1,2,3,4,2,5,6,2]
names.extend(n1)
print(names)

# 7.取出names列表中索引4-7的元素
g1=names[4:8]
print(g1)

# 8.取出names列表中索引2-10的元素，步长为2
g2=names[2:11:2]
print(g2)

# 9.取出names列表中最后3个元素
g3=names[-3:]
print(g3)

# 10.循环names列表，打印每个元素的索引值，和元素
count=0
for i in names:
print(count,'-',i)
count+=1

for i in enumerate(names):
print(type(i))
print(i)

for index,i in enumerate(names):
print(index,', ',i)

 

# 11.循环names列表，打印每个元素的索引值，和元素，当索引值 为偶数时，把对应的元素改成-1
count=0
for i in names:
if count%2==0:
print(count, ' ', -1)
else:
print(count,' ',i)
count+=1

for index,i in enumerate(names):
if index%2==0:
print(index,', ',-1)
else:
print(index,', ',i)

for index,i in enumerate(names):
if index%2==0:
names[index]=-1

print(names)

# 12.names里有3个2，请返回第2个2的索引值。不要人肉数，要动态找(提示，找到第一个2的位置，在此基础上再找第2个)
names2=names.copy()
names2[names2.index(2)]='displace'
print(names)
print(names2)
print(names2.index(2))

print(names)
idx1=names.index(2)
idx2=names[idx1+1:].index(2)
idx3=idx1+idx2+1
print(idx3,names[idx3])

 

# 13.现有商品列表如下:
# products = [ ['Iphone8',6888],['MacPro',14800], ['小米6',2499],['Coffee',31],['Book',80],['Nike Shoes',799] ]
# 需打印出这样的格式：
#
# ---------商品列表----------
# 0. Iphone8 6888
# 1. MacPro 14800
# 2. 小米6 2499
# 3. Coffee 31
# 4. Book 80
# 5. Nike Shoes 799

products=[['Iphone8',6888],['MacPro',14800],['小米6',2499],['Coffee',31],['Book',80],['Nike shoes',799]]
print('----------商品列表---------')
for i in products:
print(products.index(i),'. ',i[0],' ',i[1])

for index,p in enumerate(products):
print('%s. %s %s' % (index,p[0],p[1]))

 

14. 写一个循环，不断的问用户想买什么，用户选择一个商品编号，就把对应的商品添加到购物车里， 最终用户输入q退出时，打印购物车里的商品列表

products = [ ['Iphone8',6888],['MacPro',14800], ['小米6',2499],['Coffee',31],['Book',80],['Nike Shoes',799] ]
cart=[]
exit_flag=False
while not exit_flag:
print('-----------products list---------------')
for index,p in enumerate(products):
print('%s. %s %s' % (index,p[0],p[1]))
label=input('please input the number which you want to buy (q=exit) :')
if label.isdigit()==True:
if int(label) >=0 and int(label)<len(products):
cart.append(products[int(label)])
print('this has been added to cart: ',products[int(label)])
else:
print('there is not this products.')
elif label=='q':
if len(cart)>0:
print('your cart:')
for index,p in enumerate(cart):
print('%s. %s %s' % (index,p[0],p[1]))
else:
pass
exit_flag=True