python学习之元组

######元组######

1.为什么需要元组?

比如:打印用户的姓名

In [1]: user1 = “juff 8 male”

In [2]: user1[0:4]

Out[2]: ‘juff’

结论:字符串中操作提取姓名/年龄/性别的方式不方便,诞生元组.

2.元组的定义

•- 定义空元组 tuple = ()

•- 定义单个值的元组 tuple = (fentiao,)

•- 一般的元组 tuple = (fentiao, 8, male)

In [3]: tuple = ()

In [6]: tuple = (“baidu”,)

In [7]: tuple = (“baidu”,”18”,”male”)



3.元组特性

• 不能对元组的值任意更改;

In [8]: tuple[0] = (“haha”)

TypeError Traceback (most recent call last)

in ()

—-> 1 tuple[0] = (“haha”)

TypeError: ‘tuple’ object does not support item assignment

• 对元组分别赋值,引申对多个变量也可通过元组方式分别赋值

In [10]: name,age,gender = tuple

In [11]: print name,age,gender

baidu 18 male



• 可以更改元组内列表的值

In [13]: t1 = ([‘172.25.254.108’,’172.25.0.250’],’server8.example.com’)

In [14]: t1[0][0] = ‘172.25.254.8’

In [15]: print t1

([‘172.25.254.8’, ‘172.25.0.250’], ‘server8.example.com’)



4.元组的操作

元组也属于序列,可执行的操作如:索引、切片、重复、连接和查看长度

In [16]: t2 = (‘1’,’2’,’3’)*3

In [17]: print t2

(‘1’, ‘2’, ‘3’, ‘1’, ‘2’, ‘3’, ‘1’, ‘2’, ‘3’)

In [18]: t3 = (‘hi’,’tom’)

In [19]: t4 = (‘how’,’are’,’you’)

In [20]: print t3 + t4

(‘hi’, ‘tom’, ‘how’, ‘are’, ‘you’)

In [21]: len(t3)

Out[21]: 2

In [22]: len(t4)

Out[22]: 3



删除元组

In [23]: t1

Out[23]: ([‘172.25.254.8’, ‘172.25.0.250’], ‘server8.example.com’)

In [24]: del(t1)

In [25]: t1

NameError Traceback (most recent call last)

in ()

—-> 1 t1

NameError: name ‘t1’ is not defined



5.元组的方法

• t.count(value)–>int 返回value在元组中出现的次数;

In [26]: t2

Out[26]: (‘1’, ‘2’, ‘3’, ‘1’, ‘2’, ‘3’, ‘1’, ‘2’, ‘3’)

In [27]: t2.count(“1”)

Out[27]: 3



• t.index(value) 返回value在元组中的偏移量(即索引值)