python变量

id() -- 可以查看变量指向内存的地址

 

//进入python界面
[root@localhost test1]# ipython
Python 2.6.6 (r266:84292, Nov 22 2013, 12:11:10)
Type "copyright", "credits" or "license" for more information.

IPython 1.2.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: a = 123

In [2]: id(a)
Out[2]: 135958416

In [3]: a =456

In [4]: id(a)
Out[4]: 139897836

 

赋值为字符串，需要用 单引号  ''

 

type() --可以查看此变量是什么类型的

 

 

In [5]: 4/3
Out[5]: 1

In [6]: 4.0/3
Out[6]: 1.3333333333333333
--得到小数

In [7]: 4.0//3
Out[7]: 1.0
--整除 （只得整数）

In [8]: 19%2
Out[8]: 1
--取余

In [9]: 2**3
Out[9]: 8
--乘方 表示 2^3

 

In [10]: 1 >2
Out[10]: False
--不成立 则返回false

In [11]: 1< 2
Out[11]: True

 

In [13]: 1==2 and 2<1
Out[13]: False

In [14]: 1==2 or 2>1
Out[14]: True

In [15]: not 1==1
Out[15]: False

 

====================================

Tranning:

写一个四则运算器

1.要求从键盘读取数字

2. 分清楚input() and raw_input()的区别

/* 1. input() */
In [16]: input("please input: ")
please input: 11
Out[16]: 11

In [17]: input("please input: ")
please input: abc
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-17-dd86387934e0> in <module>()
----> 1 input("please input: ")

<string> in <module>()

NameError: name 'abc' is not defined

/*    出现错误~~ 因为不是输入数字，输入字符串要加入单引号或双引号。 */

In [18]: input("please input: ")
please input: 'abc'
Out[18]: 'abc'

===========================================
/* 2. raw_input() */
In [19]: raw_input("please input: ")
please input: sdjhsjh
Out[19]: 'sdjhsjh'

In [20]: raw_input("please input: ")
please input: 234
Out[20]: '234'

 

[root@localhost test1]# vi 3.py
//ADD
#!/usr/bin/python

num1 = input("Please input a number: ")
num2 = input("Please input a number: ")

print "%s + %s = %s" % (num1, num2, num1+num2)
print "%s - %s = %s" % (num1, num2, num1-num2)
print "%s * %s = %s" % (num1, num2, num1*num2)
print "%s / %s = %s" % (num1, num2, num1/num2)

[root@localhost test1]# python 3.py
Please input a number: 2
Please input a number: 3
2 + 3 = 5
2 - 3 = -1
2 * 3 = 6
2 / 3 = 0