Python-数据结构

List

List中的内容并不一定只有一种类型，一个List中可能既有number,又有string，还可能有子List

List用[]表示

List的基本方法有:append,sort等

要从一个List中删除某元素，可以使用del函数（它不是List的方法）

#!/usr/bin/python

mylist = ['apple','pear','banana']
print 'mylist is',mylist
mylist.sort()
print 'after sort, mylist is',mylist
first = mylist[0]
del(mylist[0])
print 'have bought',first,', now remains',
for item in mylist:
print item,

output:

mylist is ['apple', 'pear', 'banana']
after sort, mylist is ['apple', 'banana', 'pear']
have bought apple , now remains banana pear

Tuple

里面的元素不可更改，tuple中可以有子tuple

Tuple用()表示

空Tuple用()表示

只含一个元素的Tuple要在该元素后面加上[,] e.g. one_elem_tuple = (2,)

#!/usr/bin/python

old_zoo = ('tiger','lion','elephant')
print 'All animals in the old_zoo are',old_zoo
print 'Number of animals in the old_zoo is',len(old_zoo)
new_zoo = ('monkey','panda',old_zoo)
print 'All animals in the new_zoo are',new_zoo
print 'Number of animals in the new_zoo is',len(new_zoo)-1+len(new_zoo[2])
print 'Animals bought from the old_zoo are',new_zoo[2]
print 'The last animal bought from the old_zoo is',new_zoo[2][2]

output:

All animals in the old_zoo are ('tiger', 'lion', 'elephant')
Number of animals in the old_zoo is 3
All animals in the new_zoo are ('monkey', 'panda', ('tiger', 'lion', 'elephant'))
Number of animals in the new_zoo is 5
Animals bought from the old_zoo are ('tiger', 'lion', 'elephant')
The last animal bought from the old_zoo is elephant

Dictionary

键值对

key必须唯一

key只能用【不可改变】的对象(e.g. string),value可以用【不可改变或者可改变】的对象

d={key1:value1,key2:value2,...}

帮助手册：help(dict)

#!/usr/bin/python
ab = {'John':'John@163.com',
'Bill':'Bill@qq.com',
'Lily':'Lily@sohu.com'
}

print 'John\'s address is',ab['John']
del ab['Bill']
print 'After del, there are {0} contacts in the address-book'.format(len(ab))
for name,address in ab.items():
print name,address
ab['Rose']='Rose@sina.com'
if 'Rose' in ab: #OR ab.has_key('Rose')
print 'Rose\'s address is',ab['Rose']

output:

John's address is John@163.com
After del, there are 2 contacts in the address-book
John John@163.com
Lily Lily@sohu.com
Rose's address is Rose@sina.com

items方法返回一个由tuple组成的list,每个tuple包含两个元素:key和value

序列：list,tuple,string

主要特点：成员测试（【是否属于该序列】的表达式），下标操作

切片

eg. a[1:4] 取1至3
a[1:] 从1取到结尾
a[:4] 从开头到3
a[::2] 从开头到结尾，每2步一取

a[::-1] 从尾到头倒过来取
a[4:1:-1] 从4到2倒过来取
a[-1] 取最后一个字符

Set

>>> bri = set(['brazil','russia','india'])
>>> 'india' in bri
True
>>> 'usa' in bri
False
>>> bric = bri.copy()
>>> bric.add('china')
>>> bric.issuperset(bri)
True
>>> bri.remove('russia')
>>> bri & bric
set(['brazil', 'india'])

当创建一个对象并将它赋值给一个变量时，变量名指向存放对象的内存。

e.g.

shoplist = ['apple','mango','carrot','banana']

mylist = shoplist #shoplist和mylist指向同一内存。

del shoplist[0] #此时shoplist和mylist都少了第一个元素，因为他们指向的是同一内存。

mylist = shoplist[:]

del shoplist[0] #此时shoplist少了第一个元素，而mylist不变

以上规则对序列或复杂对象适用，对简单对象不适用（e.g. 整数）。

实际上，对于a=4;b=a;a=5来说，a指向了一个新的内存，而b还是指向原先的内存，因此b的值不变。只有改变了共同的内存，才会同时改变两个变量。

String

所有的string类型数据都是class str的对象，查看该类的更多方法，使用help(str)