python ----- 数据类型

#python2

>>> a = 13

>>> a

13

>>> type(a)

<type 'int'>        //整型

>>> a = 1234124512512341235124512512

>>> type(a)

<type 'long'>     //长整型

 

 

#python3

>>> a = 13

>>> type(a)

<class 'int'>

>>> a = 1245123512512561251245124124124

>>>

>>> type(a)

<class 'int'>

 

>>> a = 'hello'

>>> a

'hello'

>>> a.center(40)

'                 hello                  '

>>> a.center(40,'*')                                       //按照一定格式输出

'*****************hello******************'

>>> print("学生管理系统".center(50,'-'))

----------------------学生管理系统----------------------

>>> print("学生管理系统".center(50,'*'))

**********************学生管理系统**********************

 

 

 

>>> 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'

 

#删除内存中的变量

>>> 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

 

#布尔数据类型

>>> a = 'hello'

>>> bool(a)

True

>>> bool(0)

False

>>> b = ''

>>> b

''

>>> bool(b)

False