python_bomb----数据类型

数值类型

1.整形

Python 2.7.5 (default, Feb 11 2014, 07:46:25) 
>>> aint=3
>>> type(aint)
<type 'int'>


Python 3.6.4 (default, Aug  6 2018, 22:54:20) 
>>> aint=3
>>> type(aint)    
<class 'int'>

2.长整形

python2#有长整形
>>> along=1728219876932764873264934692
>>> type(along)
<type 'long'>


python3#没有长整形
>>> along=1728219876932764873264934692
>>> type(along)
<class 'int'>

3.浮点型

1.344,12000000=12e6=1.2e7=0.12e7,0.012=1.2e-2

python2
>>> afloat=12e3
>>> afloat
12000.0
>>> type(afloat)
<type 'float'>

python3
>>> afloat=12e3
>>> type(afloat)
<class 'float'>

4.复数类型

acomplex=3j+8
type(acomplex)
<type 'complex'>

查看帮助：可以使用什么方法，实现什么功能？

help(acomplex)

dir(acomplex)
['__abs__', '__add__', '__class__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__eq__', '__float__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__int__', '__le__', '__long__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__nonzero__', '__pos__', '__pow__', '__radd__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rmod__', '__rmul__', '__rpow__', '__rsub__', '__rtruediv__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', 'conjugate', 'imag', 'real']

>>> acomplex.conjugate()    #共轭
(8-3j)
>>> acomplex.imag    #虚部
3.0
>>> acomplex.real    #实部
8.0

初学阶段，避免使用"__"开头的内置功能

5.字符串数据类型

>>> astring="hello"
>>> type(astring)
<type 'str'>
>>> dir(astring)
['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '_formatter_field_name_split', '_formatter_parser', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']
>>> help(astring.center)
>>> astring.center(40,"*")
'*****************hello******************'
>>> print("学生管理系统".center(40,'*'))
***********学生管理系统***********

数据类型的转换

-在python中，所有的数据类型都可以作为内置函数，用来转换数据类型：

>>> int(3.10)
3
>>> str(3)   
'3'
>>> type(str(3))
<class 'str'>
>>> float(3)
3.0
>>> complex(2)
(2+0j)

如何删除内存中的变量

>>> afloat=2e12
>>> del afloat
>>> afloat
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'afloat' is not defined

布尔数据类型

bool:只有两个值(True,Flase)

>>>a = 1
>>> bool(a)
True
>>> bool(0)
False
>>> name = 'we'
>>> bool(a)
True

运算符

1.算术运算符

+,-,,*,/,%,//

2.赋值运算符

=,+=,-=,/=,%=,*=

3.关系运算符

,>=,<,<=,!=,==

4.逻辑运算符

逻辑与and
逻辑或or
逻辑非not

python2

>>> 5/2
2
>>> 100/300
0

>>> 5/2.0
2.5
>>> 100/300.0
0.3333333333333333

>>> from __future__ import division
>>> 5/3
1.6666666666666667

python3

vim empty.py

#判断输入为空时，输出"Error"
value=input("请输入：")
if not value:
    print("Erros")