A. Notes
不论在python2.7还是python3.6版本中，单行注释都是“#”,多行注释是“ “”" ”
note:
Take the time to write python vim program:
execute the content using python3.6 python2.7 version version, you will find there has been an error, indicating that the two versions of the format is not universal:
the default input 1. When using a python 2.7 Python
2.python 'Hello World' is python2.7 version format, python ( 'hello world') is the version of the format python3.6
3.pyhton3.6 default usage utf-8, python2.7 specify code # Coding: UTF-8
4. best when writing the file name ends with .py, it would be more standardized
5.python2.7 some formats can be used python3.6 version, but in turn can not.
Two: python O
python2.7 inside:
>>> import getpass
>>> num=getpass.getpass('请输入密码：')
请输入密码：
>>> num
'redhat'
>>>
>>>
>>>
>>> age=raw_input('请输入年龄：')
请输入年龄：18
>>> age
'18'
>>> type(age)
<type 'str'>
>>> int(age)
18
>>> age > 19
True
>>> age
'18'
>>> age=20
>>> age > 19
True
>>> age=raw_input('请输入年龄：')
请输入年龄：18
>>> age
'18'
>>> int(age) > 19
False
Formatted output
String% s
% d shaping
% f float
In [1]: name = 'westos'
In [2]: age = 11
In [3]: print('%s的年龄为%d' %(name,age))
westos的年龄为11
In [4]: name = 'redhat'
In [5]: print('%s的年龄为%d' %(name,age))
redhat的年龄为11
ln [8]: money = 8576.123123
In [9]: print('%s本月的工资为%f' %(name,money))
redhat本月的工资为8576.123123
In [10]: money = 7000
In [11]: print('%s本月的工资为%f' %(name,money))
redhat本月的工资为7000.000000
In [12]: print('%s本月的工资为%.2f' %(name,money))
redhat本月的工资为7000.00
In [13]: print('%s本月的工资为%.3f' %(name,money))
redhat本月的工资为7000.000
In [15]: sid = 1
In [16]: print('%s的学号为%d' %(name,sid))
redhat的学号为1
In [17]: print('%s的学号为130%d' %(name,sid))
redhat的学号为1301
In [18]: print('%s的学号为111%d' %(name,sid))
redhat的学号为1111
In [19]: print('%s的学号为130%d' %(name,sid))
redhat的学号为1301
In [20]: print('%s的学号为130%.3d' %(name,sid))
redhat的学号为130001
In [21]: print('%s的学号为130%.5d' %(name,sid))
redhat的学号为13000001
In [22]: scale = 0.1
In [23]: print('数据比例是 %.2f' %(scale * 100))
数据比例是 10.00
In [24]: print('数据比例是 %.2f%%' %(scale * 100))
数据比例是 10.00%
III. Variables
Variable naming rules:
Hump command method:
1. Big Hump: The first letter of each word is capitalized LastName FirstName
2. small hump: the first word beginning with a lowercase letter, the first letter of subsequent words capitalized firstName lastName
#str:表示一个字符串类型
In [1]: name = '彭于晏'
In [2]: name
Out[2]: '彭于晏'
int:表示一个整形
In [3]: age = 18
In [4]: age
Out[4]: 18
#bool：表示一个布尔型，真：True 假：False
In [5]: gender = True
In [6]: gender
Out[6]: True
#float:表示一个浮点型
In [7]: height = 180.5
In [8]: height Out[8]: 180.5
In [9]: price = 8.5
In [10]: weight = 7.5
In [11]: money = price * weight
In [12]: money
Out[12]: 63.75
#变量名只有在第一次出现的时候，才是定义变量
In [13]: money = money - 5
In [14]: money
Out[14]: 58.75
IV: Data Types
python3.6
>>> a = 13
>>> type(a)
<class 'int'>
>>> a = 1245123512512561251245124124124
>>>
>>> type(a)
<class 'int'>
python2.7
>>> a = 13
>>> a
13
>>> type(a)
<type 'int'>
>>> a = 1234124512512341235124512512
>>> type(a)
<type 'long'>
>>> a = 1
>>> float(a)
1.0
>>> b = 2.3
>>> int(b)
2
>>> float(b)
2.3
>>> str(b)
'2.3'
>>> str = 'westos'
>>> float(str)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: could not convert string to float: 'westos'
Delete variables in memory
>>> a = 1.2
>>> a
1.2
>>> del a
>>> a
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined
Boolean data type (not empty and 0 are true)
>>> a = 'hello'
>>> bool(a)
True
>>> bool(0)
False
>>> b = ''
>>> b
''
>>> bool(b)
False
