Python之变量--初识练习

变量命名：见名知意

由字母、数字、下划线组成
不能以数字开头
不能和关键字重名

驼峰命名法：
1.大驼峰：FirstName
2.小驼峰：firstName

输入输出练习

In [1]: 1                             ##无定义，输入等于输出                         
Out[1]: 1

In [2]: 2                                                               
Out[2]: 2

In [3]: type(1)                 ##定义输出1的类型                                        
Out[3]: int						 ##整数型

In [4]: type(2)                                                         
Out[4]: int

In [5]: type(111111111111111111111111111111111111)                      
Out[5]: int

In [6]: type(-1)                                                        
Out[6]: int

In [7]: type(1.1)            ## 定义输出1.1的类型                                           
Out[7]: float		    		##浮点数

In [8]: type(1.111111111111111111111111)                                
Out[8]: float

#python2.x
Type "help", "copyright", "credits" or "license" for more information.
>>> input('Num:')
Num:a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<string>", line 1, in <module>
NameError: name 'a' is not defined
>>> input('Num:')
Num:2
2
>>> raw_input('Num:')
Num:a
'a'
>>> raw_input('Num:')
Num:1
'1'
>>> 

 #python3.x
    >>> input('Num:)
      File "<stdin>", line 1
        input('Num:)
                   ^
    SyntaxError: EOL while scanning string literal
    >>> input('Num:')
    Num:a
    'a'
    >>> input('Num:')
    Num:2
    '2'
    >>> num = input()
   12
  >>> num
   '12'
  >>> num > 19
  Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  TypeError: '>' not supported between instances of 'str' and 'int'
  >>> int(num) > 19
  False
  >>> int(num) < 19
  True
  >>> 

>>> name = 'li'
>>> age = '20'
>>> print('%s的年龄是%d岁' %(name,age))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: %d format: a number is required, not str

>>> name = 'li'
>>> age = 20
>>> print('%s的年龄是%d岁' %(name,age))
li的年龄是20岁

>>> ship = 168.999999
>>> print('%s的奖学金是%f' %(name,ship))
li的奖学金是168.999999
>>> ship=700
>>>  print('%s本月的奖学金为%f' %(name,ship))
  File "<stdin>", line 1
    print('%s本月的奖学金为%f' %(name,ship))
    ^
IndentationError: unexpected indent
>>> print('%s本月的奖学金为%f' %(name,ship))
li本月的奖学金为700.000000
>>> print('%s本月的奖学金为%2f' %(name,ship))
li本月的奖学金为700.000000
>>> print('%s本月的奖学金为%.2f' %(name,ship))
li本月的奖学金为700.00
>>> print('%s本月的奖学金为%.3f' %(name,ship))
li本月的奖学金为700.000
>>> 

>>> studentid=1
>>>  studentid=9
  File "<stdin>", line 1
    studentid=9
    ^
IndentationError: unexpected indent
>>> studentid=9
>>> print('%s的学号为130%d' %(name,studentid))
li的学号为1309
>>> print('%s的学号为130%.3d' %(name,studentid))
li的学号为130009
>>> scale = 0.2
>>> print('比例是 %.2f' %scale)
比例是 0.20
>>> print('比例是 %.2f' %(scale * 100))
比例是 20.00
>>> print('比例是 %.2f%%' %(scale * 100))
比例是 20.00%
>>> 

# 
#- 输入学生学号;
#- 依次输入学生的三门科目成绩;
#- 计算该学生的平均成绩, 并打印;
#- 平均成绩保留两位小数点;
#- 计算该学生语文成绩占总成绩的百分之多少？并打印。

ID = input("学生ID：")
Chinese = float(input("语文成绩："))
Math = float(input("数学成绩："))
English = float(input("英语成绩："))

#总成绩
SumScore = Chinese + Math + English

#平均成绩
AvgScore = SumScore / 3

#百分比
ChinesePercent = ( Chinese / SumScore ) * 100

print("%s的平均成绩为%.2f" %(ID,AvgScore))
print("语文成绩占总成绩的%.2f%%" %ChinesePercent)