python数据类型

数据类型
数字:int ,float,complex
布尔:True,False
字符串:'',"", '''....'''
列表 list:[] 带索引有序的,字符串操作的行为都适合它
元组 tuple:()
字典 dict:{'a':1}
集合 set:{'a','b'}

数字：
int ,float,Complex

>>> a=1
>>> type(a)
<class 'int'>
>>> p=3.141592653
>>> p
3.141592653
>>> type(p)
<class 'float'>
>>> c=3+4j
>>> d=4+2j
>>> c+d
(7+6j)
>>> type(c)
<class 'complex'>
>>> a+p
4.141592653
>>> a+c
(4+4j)
>>> p*100000000000000000
3.141592653e+17
>>> 0.23/1000000000000000
2.3e-16

bool(布尔值/逻辑值)

对与错、真与假、空与非空
只包含2个值
True:表示非空的对象(string,tuple,list,set,dictonary等以及所有非0数)
False:表示0,None空的对象等
作用:主要用于判断语句中
一个字符串是否是空的
一个运算结果是否为0
一个表达式是否可用
注意('')与[''],{''},{'':''}的区别
('')为假,[''],{''},{'':''}为真

bool()

n [82]: bool('')
Out[82]: False

In [83]: bool(' ')
Out[83]: True

In [84]: bool(0)
Out[84]: False

In [85]: bool('0')
Out[85]: True

In [89]: a=()

In [90]: type(a)
Out[90]: tuple

In [91]: bool(a)
Out[91]: False

In [92]: a=('')

In [93]: bool(a)
Out[93]: False

In [94]: a=(' ')

In [95]: bool(a)
Out[95]: True

In [104]: bool([])
Out[104]: False

In [105]: bool([''])
Out[105]: True

In [113]: bool({})
Out[113]: False

In [114]: bool({''})
Out[114]: True

In [121]: a={'':''}

In [122]: type(a)
Out[122]: dict

In [123]: bool(a)
Out[123]: True

 isinstance(object, classinfo)

如果参数object是classinfo的实例,或者object是classinfo类的子类的一个实例， 返回True
如果object不是一个给定类型的的对象,则返回结果总是False。
如果classinfo不表示一个类(类型对象),那么它要么是一个类的元组, 或者递归地包含这样的（由数据类型构成的）元组.其他的序列类型是不被允许的。
如果classinfo不是一种数据类型或者由数据类型构成的元组，将引发一个TypeError异常

len()

In [15]: type(1)
Out[15]: int

In [16]: isinstance(1,type(1))
Out[16]: True

In [17]: isinstance(1.0,int)
Out[17]: False

In [18]: isinstance(1.0,float)
Out[18]: True

In [19]: isinstance((),tuple)
Out[19]: True

In [20]: isinstance({},dict)
Out[20]: True

In [21]: isinstance([],list)
Out[21]: True

In [22]: isinstance({''},set)
Out[22]: True

In [23]: isinstance({'':''},dict)
Out[23]: True

len()
In [24]: len('a')
Out[24]: 1

In [25]: len(['a','b'])
Out[25]: 2

In [26]: len(['aa','b'])
Out[26]: 2

In [27]: len((1,2,'a'))
Out[27]: 3

In [28]: len({'a':'ajax','p':'php'})
Out[28]: 2

In [31]: len((1,2,'a',{'a':'ajax','b':[1,2,'aaa']}))
Out[31]: 4

字符串：

1.单引号
'字符串'
2.双引号
"字符串"
3.三重单引号(类似注释)
,,,
大段数据
定义在三重引号(单或者双)里
术语叫docstring
,,,

In [1]: s='hello word'

In [2]: s
Out[2]: 'hello word'

In [3]: type(s)
Out[3]: str

In [4]: say='tom say:"let\'s go"'

In [5]: say
Out[5]: 'tom say:"let\'s go"'

In [6]: print(say)
tom say:"let's go"

say='tom say:let\'s go \n lily:ok'
print(say)
tom say:let's go
 lily:ok
 如果不使用\n来保持换行
 
In [12]: say1=''' tom:let'go!
    ...: jim:wait me a moment ,I"will finish soon
    ...: tom:ok
    ...: '''
 print(say1)
 tom:let'go!
jim:wait me a moment ,I"will finish soon
tom:ok
In [15]: say1
Out[15]: ' tom:let\'go!\njim:wait me a moment ,I"will finish soon\ntom:ok\n'

特殊符号需要转义
定义原始字符串
使用
r "\ 没有意义但不能在结尾"

In [21]: str1=r"let's go\t ok"

In [22]: str1
Out[22]: "let's go\\t ok"

In [23]: str2="let's go \t ok"

In [24]: str2
Out[24]: "let's go \t ok"

In [25]: print(str1)
let's go\t ok

In [26]: print(str2)
let's go         ok

字符串的拼接
字符串+字符串,或者字符串*数字 ,不支持减法和数字的除法

In [28]: a='1'
In [29]: b=2
In [30]: a+b
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-30-ca730b97bf8a> in <module>()
----> 1 a+b

TypeError: can only concatenate str (not "int") to str

In [31]: a+str(b)
Out[31]: '12'

In [32]: b+int(a)
Out[32]: 3

In [33]: a*3
Out[33]: '111'
In [34]: str(b)-a
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-34-df4abb960107> in <module>()
----> 1 str(b)-a

TypeError: unsupported operand type(s) for -: 'str' and 'str'

字符串分片和索引
成员关系操作符
in,not in

In [40]: 'hello' in 'hello world'
Out[40]: True
 lang="php js python"
 >>> if "php" in lang :
...     print("php is ok")
...     print("ok is php")
...
php is ok
ok is php
>>>

字符串截取
String[i:j:k]
string[i]
string[i:j]
string[i:]
string[:j]
string[:]

i表示从第某个位置开始
j到第几个
k表示每隔几个取一个
对i,j前闭后开(到j但是不包含第j位置上的)

In [7]: s="hello world"

In [8]: s[0]
Out[8]: 'h'

In [9]: s[-1]
Out[9]: 'd'

In [10]: s[0:5]
Out[10]: 'hello'

In [13]: s[6:]
Out[13]: 'world'

In [18]: s[1:2]
Out[18]: 'e'

In [20]: s[:5]
Out[20]: 'hello'

In [24]: s[-1:]
Out[24]: 'd'

In [25]: s[-5:]
Out[25]: 'world'

In [26]: s[-5:-1]
Out[26]: 'worl'

In [27]: s[-5:0]
Out[27]: ''

In [28]: s[-5:-2]
Out[28]: 'wor'

In [29]: s[:]
Out[29]: 'hello world'

In [30]: s[::1]
Out[30]: 'hello world'

In [31]: s[::2]
Out[31]: 'hlowrd'

In [32]: s[2:8:2]
Out[32]: 'low'

格式化字符串
%s
%d
string="str %s,%d"
string_templae % "替换的数据"

In [34]: note="I have %d subjects,and i love %s"

In [35]: note
Out[35]: 'I have %d subjects,and i love %s'

In [36]: note %(5,'english')
Out[36]: 'I have 5 subjects,and i love english'

In [37]: d1=(5,'english')

In [38]: d2=(8,"math")

In [39]: note %d1
Out[39]: 'I have 5 subjects,and i love english'

In [40]: note %d2
Out[40]: 'I have 8 subjects,and i love math'

In [41]: type(d1)
Out[41]: tuple

 字符串的遍历

In [35]: s="abcdefg"

In [36]: s[0]
Out[36]: 'a'

In [37]: for i in s:
    ...:     print(i)
    ...:
a
b
c
d
e
f
g

 字符串对象方法

http://www.cnblogs.com/HKUI/articles/8970041.html

列表list操作

list.append()
list.insert()
list.extend()
list.pop()
list.remove()
list,sort()
list.sorted()

sum([1,2,3]) 对整型列表求和

In [28]: a=[1,2,3,'aa','bb']

In [29]: a[:2]
Out[29]: [1, 2]

In [30]: a+['c',"d"]
Out[30]: [1, 2, 3, 'aa', 'bb', 'c', 'd']

In [31]: a*2
Out[31]: [1, 2, 3, 'aa', 'bb', 1, 2, 3, 'aa', 'bb']

In [32]: a-[1]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-32-e428de774a53> in <module>()
----> 1 a-[1]

TypeError: unsupported operand type(s) for -: 'list' and 'list'

In [33]: a+[1]
Out[33]: [1, 2, 3, 'aa', 'bb', 1]

列表元素可变,字符串可元组不可变

In [38]: s
Out[38]: 'abcdefg'

In [39]: s[0]='k'
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-39-ab359d50dcca> in <module>()
----> 1 s[0]='k'

TypeError: 'str' object does not support item assignment

In [40]: s1=['a','b','c','d']

In [41]: s1
Out[41]: ['a', 'b', 'c', 'd']

In [42]: s1[0]='k'

In [43]: s1
Out[43]: ['k', 'b', 'c', 'd']

In [44]: s1
Out[44]: ['k', 'b', 'c', 'd']

In [46]: s1.append("e")

In [47]: s1
Out[47]: ['k', 'b', 'c', 'd', 'e']

In [48]: s1.insert(1,'o')

In [49]: s1
Out[49]: ['k', 'o', 'b', 'c', 'd', 'e']
In [50]: a=["a",'b','c']

In [51]: b=["d",'e','f']

In [52]: a.extend(b)

In [53]: a
Out[53]: ['a', 'b', 'c', 'd', 'e', 'f']

In [56]: a
Out[56]: ['a', 'b', 'c']

In [57]: b=["c",'d','e']

In [58]: a.append(b)

In [59]: a
Out[59]: ['a', 'b', 'c', ['c', 'd', 'e']]

In [60]: a[1]
Out[60]: 'b'

In [61]: a[3]
Out[61]: ['c', 'd', 'e']

In [62]: a[3][1]
Out[62]: 'd'
In [65]: a.remove('c')

In [66]: a
Out[66]: ['a', 'b', ['c', 'd', 'e']]

In [67]: a.pop(-2)
Out[67]: 'b'

In [68]: a
Out[68]: ['a', ['c', 'd', 'e']]

In [70]: n
Out[70]: [2, 1, 3, 5, 7]
In [72]: n.sort()

In [73]: n
Out[73]: [1, 2, 3, 5, 7]

In [87]: n=[6,7,2,1]

In [88]: n.sort(reverse=True)

In [89]: n
Out[89]: [7, 6, 2, 1]

In [90]: n=[6,7,2,1]

In [91]: sorted(n)
Out[91]: [1, 2, 6, 7]

In [92]: n
Out[92]: [6, 7, 2, 1]

 列表元素可变和内存

In [109]: box
Out[109]: ['a', 'b', 'c']

In [110]: id(box)
Out[110]: 114256351368

In [111]: x='x'

In [112]: id(x)
Out[112]: 114215701840

In [113]: id(box[0])
Out[113]: 114216537928

In [114]: box[0]='x'

In [115]: id(box)
Out[115]: 114256351368

In [116]: id(box[0])
Out[116]: 114215701840

 列表的赋值和复制

值传递和引用传递

list(list)

 

In [21]: box=['a','b','c']

In [22]: id(box)
Out[22]: 231716803400

In [23]: b1=box

In [24]: id(b1)
Out[24]: 231716803400

In [25]: b2=list(box)

In [26]: id(b2)
Out[26]: 231715699464

In [27]: b1[0]="x"

In [28]: box
Out[28]: ['x', 'b', 'c']

In [29]: b2[1]="bb"

In [30]: box
Out[30]: ['x', 'b', 'c']

In [31]: b2
Out[31]: ['a', 'bb', 'c']

元组

里面元素一旦定义不可变
拆分 x,y=(v1,v2) 必须个数对应
操作:同字符串,列表

In [94]: t=("x",'y',['a','b'])

In [95]: type(t)
Out[95]: tuple

In [96]: x,y,z=t

In [97]: x
Out[97]: 'x'

In [98]: y
Out[98]: 'y'

In [99]: z
Out[99]: ['a', 'b']


In [101]: t[0]
Out[101]: 'x'

In [102]: t[0]="xx"
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-102-4199c23e8e8e> in <module>()
----> 1 t[0]="xx"

TypeError: 'tuple' object does not support item assignment

In [104]: a=1

In [105]: b=2

In [106]: t1=(a,b)

In [107]: t1
Out[107]: (1, 2)