python元组

In [1]: my_strs=("a","bbb",‘ccc‘)

In [2]: my_strs
Out[2]: (‘a‘, ‘bbb‘, ‘ccc‘)

In [3]: my_strs[0]
Out[3]: ‘a‘

In [4]: my_strs[-1]
Out[4]: ‘ccc‘

In [5]: my_strs[3]
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-5-978c5894f0f0> in <module>()
----> 1 my_strs[3]

IndexError: tuple index out of range

In [6]: my_strs[0]="aaa"
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-4152d9453e33> in <module>()
----> 1 my_strs[0]="aaa"

TypeError: ‘tuple‘ object does not support item assignment

In [8]: len(my_strs)  #定义好了元组，长度就固定了。
Out[8]: 3


In [11]: name=[1,2,3,4]

In [12]: my_tuple=(100,200,name) #元组中的元素为列表

In [13]: my_tuple
Out[13]: (100, 200, [1, 2, 3, 4])

In [15]: my_tuple[2]
Out[15]: [1, 2, 3, 4]

In [16]: my_tuple[2][0]=100 #元组中若包含列表，列表本身是可以修改的。

In [17]: my_tuple
Out[17]: (100, 200, [100, 2, 3, 4])

In [17]: my_tuple
Out[17]: (100, 200, [100, 2, 3, 4])

In [19]: my_tuple.index(100)
Out[19]: 0

In [20]: my_tuple.count(100)
Out[20]: 1

In [21]: 100 in my_tuple
Out[21]: True

In [22]: 100 not in my_tuple
Out[22]: False

In [23]: 

#用for循环实现
In [23]: for i in name:
    ...:     print(i)
    ...:     
100
2
3
4

In [24]: for i in my_tuple:
    ...:     print(i)
    ...:     
    ...:     
100
200
[100, 2, 3, 4]

In [25]: range(1,100)
Out[25]: range(1, 100)

In [26]: for i in range(1,10):
    ...:     print(i)
    ...:     
1
2
3
4
5
6
7
8
9

In [27]: c=range(1,10)

In [28]: c
Out[28]: range(1, 10)

#用while实现
In [29]: i=0

In [30]: while i<len(name):
    ...:     print(name[i])
    ...:     i+=1
    ...:     
100
2
3
4

[root@localhost ~]# python
Python 2.6.6 (r266:84292, Aug 18 2016, 15:13:37) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> c=range(1,10) 
>>> c
[1, 2, 3, 4, 5, 6, 7, 8, 9] #python2中直接返回列表
>>> exit()
[root@localhost ~]# python3
Python 3.6.5 (default, May  1 2018, 16:43:30) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-18)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> c=range(1,10)     #懒加载，只有使用访问里面的元素时才会得到一个列表，节省内存空间。 python3优化后的处理。
>>> c
range(1, 10)

In [31]: a=1 #变量a指向数值为1的内存空间；

In [32]: a
Out[32]: 1

In [33]: a=2 #变量a指向数值为2的内存空间

In [34]: a  #改变的是a的引用指向，并非将原本1的内存的值修改为2，当内存中的值没有被任何一个变量引用的时候，内存会自动回收
Out[34]: 2