python基础9 列表，元组操作

Posted 2020-09-28

本节内容：

1 列表

2 元组

3 参考网页

列表

Python内置的一种数据类型是列表：list。list是一种有序的集合，可以随时添加和删除其中的元素。

列表是我们最以后最常用的数据类型之一，通过列表可以对数据实现最方便的存储、修改等操作。

定义列表

names = [‘Michael‘, ‘Bob‘, ‘Tracy‘]

访问列表

通过索引访问

通过下标访问列表中的元素，下标从0开始计数。 使用索引时，千万注意不要越界。

>>> names[0]
‘Michael‘
>>> names[2]
‘Tracy‘

倒序访问

千万注意不要越界。

>>> names[-1] ] #倒着取，倒数第一个
‘Tracy‘
>>> names[-2] #倒着取，倒数第二个
‘Bob‘

切片：访问多个元素

name = ["cathy","jack","jerry","lucy","lily","carry","abby"]

names[1:4]  #取下标1至下标5之间的数字，包括1，不包括4
[‘jack‘, ‘jerry‘, ‘lucy‘,‘lily‘]

names[1:-1] #取下标1至-1的值，不包括-1
[‘jack‘,‘jerry‘,‘lucy‘,‘lily‘,‘carry‘]
 names[0:3] 
[‘cathy‘,‘jack‘,‘jerry‘]
names[:3] #如果是从头开始取，0可以忽略，跟上句效果一样
[‘cathy‘,‘jack‘,‘jerry‘]
 names[3:] #如果想取最后一个，必须不能写-1，只能这么写
[‘lucy‘,‘lily‘,‘carry‘,‘abby‘] 
 names[3:-1] #这样-1就不会被包含了
[‘lucy‘,‘lily‘,‘carry‘]
names[0::2] #后面的2是代表，每隔一个元素，就取一个
[‘cathy‘, ‘jerry‘, ‘lily‘,‘abby‘] 
names[::2] #和上句效果一样
[‘cathy‘, ‘jerry‘, ‘lily‘,‘abby‘]

追加

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
names.append("我是新来的")
print(names)

结果：

[‘cathy‘, ‘jack‘, ‘jerry‘, ‘lucy‘, ‘lily‘, ‘carry‘, ‘abby‘, ‘我是新来的‘]

插入

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
names.insert(2,"强行从2索引位置插入数据")
print(names)

结果：

[‘cathy‘, ‘jack‘, ‘强行从2索引位置插入数据‘, ‘jerry‘, ‘lucy‘, ‘lily‘, ‘carry‘, ‘abby‘]

修改

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
names[2] = "索引为2的位置修改"
print(names)

结果：

[‘cathy‘, ‘jack‘, ‘索引为2的位置修改‘, ‘lucy‘, ‘lily‘, ‘carry‘, ‘abby‘]

删除

• 例1 del

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
del names[2] #delete索引为2的元素
print(names)

结果：

[‘cathy‘, ‘jack‘, ‘lucy‘, ‘lily‘, ‘carry‘, ‘abby‘]

• 例2 remove()

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
names.remove("jack") #删除指定元素
print(names)

结果：

[‘cathy‘, ‘jerry‘, ‘lucy‘, ‘lily‘, ‘carry‘, ‘abby‘]

• 例3 pop()

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
names.pop() #删除列表最后一个值"abby"
print(names)

结果：

[‘cathy‘, ‘jack‘, ‘jerry‘, ‘lucy‘, ‘lily‘, ‘carry‘]

pop()方法总是删掉list的最后一个元素

#删除jerry
names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
names.pop(2) #删除列表索引为2的值
print(names)

结果：

[‘cathy‘, ‘jack‘, ‘lucy‘, ‘lily‘, ‘carry‘, ‘abby‘]

names.pop(3) IndexError: pop index out of range

扩张

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
b = [1,2,3]
names.extend(b)
print(names)

结果：

[‘cathy‘, ‘jack‘, ‘jerry‘, ‘lucy‘, ‘lily‘, ‘carry‘, ‘abby‘, 1, 2, 3]

统计

names = ["cathy","lily","jerry","lucy","lily","carry","abby"]
cnum = names.count("lily")
print(cnum)

结果： 2

排序

• 例1

names = ["cathy","jack","jerry","lucy","lily","carry","abby"]
names.sort() #排序
print(names)

结果：

[‘abby‘, ‘carry‘, ‘cathy‘, ‘jack‘, ‘jerry‘, ‘lily‘, ‘lucy‘]

• 例2

names = ["cathy","jack","jerry",1,2,3]
names.sort() #排序
print(names)

结果会报如下的错误：

names.sort() #排序
TypeError: unorderable types: int() < str()

• 例3

names = ["cathy","jack","jerry","1","2","3"]
names.sort()
print(names)

结果：

[‘1‘, ‘2‘, ‘3‘, ‘cathy‘, ‘jack‘, ‘jerry‘]

列表的排序按asii顺序排序。

反转

names = ["cathy","jack","jerry","1","2","3"]
names.reverse() #反转
print(names)

结果：

[‘3‘, ‘2‘, ‘1‘, ‘jerry‘, ‘jack‘, ‘cathy‘]

获取下标

names = ["cathy","lily","jerry","lucy","lily","carry","abby"]
nid = names.index("lily") #只返回找到的第一个下标
print(nid)

结果： 1

拷贝

Python中，对象的赋值，拷贝（深/浅拷贝）之间是有差异的。

对象赋值

在python中，对象赋值实际上是对象的引用。当创建一个对象，然后把它赋给另一个变量的时候，python并没有拷贝这个对象，而只是拷贝了这个对象的引用。 当对对象做赋值或者是参数传递或者作为返回值的时候，总是传递原始对象的引用，而不是一个副本。

list = ["cathy","jack","jerry",["bruce","85"]]
b=list
list.append(5)
list[3].append("75")
print(list)
print(b)
结果：
[‘cathy‘, ‘jack‘, ‘jerry‘, [‘bruce‘, ‘85‘, ‘75‘], 5]
[‘cathy‘, ‘jack‘, ‘jerry‘, [‘bruce‘, ‘85‘, ‘75‘], 5]

原始列表改变，被赋值的b也会做相同的改变。

浅拷贝

copy浅拷贝，没有拷贝子对象，所以原始数据改变，新copy的子对象会改变。

import copy
list = ["cathy","jack","jerry",["lily","100"]]
c=copy.copy(list)
print(list,c)

list.append(5)
print(list,c)

list[3].append(‘99‘)
print(list)
print(c)
结果：
[‘cathy‘, ‘jack‘, ‘jerry‘, [‘lily‘, ‘100‘]] [‘cathy‘, ‘jack‘, ‘jerry‘, [‘lily‘, ‘100‘]]
[‘cathy‘, ‘jack‘, ‘jerry‘, [‘lily‘, ‘100‘], 5] [‘cathy‘, ‘jack‘, ‘jerry‘, [‘lily‘, ‘100‘]]
[‘cathy‘, ‘jack‘, ‘jerry‘, [‘lily‘, ‘100‘, ‘99‘], 5]
[‘cathy‘, ‘jack‘, ‘jerry‘, [‘lily‘, ‘100‘, ‘99‘]] #里面的子对象被改变了

names = ["cathy","lily","jerry",["abby","95"]]
name_copy = names.copy()
names.append("bruce")
names[3].append("60")
print(name_copy)
print(names)
结果显示：
[‘cathy‘, ‘lily‘, ‘jerry‘, [‘abby‘, ‘95‘, ‘60‘]]
[‘cathy‘, ‘lily‘, ‘jerry‘, [‘abby‘, ‘95‘, ‘60‘], ‘bruce‘]

深拷贝

深拷贝，包含对象里面的自对象的拷贝，所以原始对象的改变不会造成深拷贝里任何子元素的改变。

import copy
names = ["cathy","lily","jerry",["abby","95"]]
d=copy.deepcopy(names)
print(names)
print(d)
names.append("jack")
names[3].append("70")
print(names)
print(d)
结果显示：
[‘cathy‘, ‘lily‘, ‘jerry‘, [‘abby‘, ‘95‘]]
[‘cathy‘, ‘lily‘, ‘jerry‘, [‘abby‘, ‘95‘]]
[‘cathy‘, ‘lily‘, ‘jerry‘, [‘abby‘, ‘95‘, ‘70‘], ‘jack‘]
[‘cathy‘, ‘lily‘, ‘jerry‘, [‘abby‘, ‘95‘]] #始终没有改变

元组

元组其实跟列表差不多，也是存一组数，只不是它一旦创建，便不能再修改，所以又叫只读列表

它只有2个方法，一个是count,一个是index，完毕。

names = ("cathy","jack","lucy","cathy")
nid = names.index("cathy")

ncnum = names.count("cathy")
print(nid)
print(ncnum)

结果：

0
2

参考网页

http://www.cnblogs.com/alex3714/articles/5717620.html

http://www.imooc.com/code/3355

http://blog.csdn.net/lixintong1992/article/details/51005546

http://www.cnblogs.com/kellyseeme/p/5525067.html

http://www.cnblogs.com/xueli/p/4952063.html

http://python.jobbole.com/82294/