python 数据类型转换

这篇文章主要介绍了常用的python数据类型转换函数,并用实际例子说明了这些函数的用法：

下面以实例来讲解：
1.int(x,[base])
int()函数把x转换为整数，不会四舍五入。

In [1]: int(5.4)
Out[1]: 5

In [2]: int(5.6)
Out[2]: 5
In [3]: int(3L)
Out[3]: 3
In [4]: int("7")
Out[4]: 7
In [5]: int("14",10)
Out[5]: 14
In [6]: int("14",12)
Out[6]: 16              #14+2

2.long(x)
long()函数把x转换为长整数，转换完成后，在数字后面加'L'

In [3]: long(24)
Out[3]: 24L

In [4]: long(200.56)
Out[4]: 200L
In [5]: long('123')
Out[5]: 123L

3.float(x)
float()函数把x转换为浮点数

In [7]: float(2)
Out[7]: 2.0
In [8]: float(12L)
Out[8]: 12.0
In [9]: float("12")
Out[9]: 12.0
In [10]: float(2.9)
Out[10]: 2.8999999999999999

4.str(x)
str()函数把x转换为字符串

In [12]: a=str(79)

In [13]: type(a)
Out[13]: str

In [14]: a
Out[14]: '79'

5.repr(x)
将对象x转换为表达式字符串

In [35]: repr([0,1,2,3])
Out[35]: '[0, 1, 2, 3]'

In [36]: repr('Hello')
Out[36]: "'Hello'"

6.tuple(s)
tuple()函数把序列对象转换成tuple。

In [37]: tuple('hello world')
Out[37]: ('h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd')

In [38]: tuple([4,5,6,1,2,3])
Out[38]: (4, 5, 6, 1, 2, 3)

7.list(s)
list()函数可将序列对象转换成列表。

In [39]: list('hello world')
Out[39]: ['h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd']

In [40]: list((1,2,3,4,5))
Out[40]: [1, 2, 3, 4, 5]

8.set(s)
转换为可变集合

In [46]: set(['hello','world'])
Out[46]: {'hello', 'world'}

In [47]: set('nihao')
Out[47]: {'a', 'h', 'i', 'n', 'o'}

9.frozenset(s)
转换为不可变集合，集合中数据不能更新

In [50]: frozenset('this is a book')
Out[50]: frozenset({' ', 'a', 'b', 'h', 'i', 'k', 'o', 's', 't'})

10.chr(x)
chr()函数返回ASCII码对应的字符串.

In [51]: print chr(65)
A

In [52]: print chr(65)+chr(97)
Aa

In [53]: print chr(23)
口

In [54]: print chr(55)
7

11.unichr(x)
将一个整数，转换为Unicode字符

In [55]: unichr(55)
Out[55]: u'7'

In [56]: unichr(123)
Out[56]: u'{'

In [57]: unichr(99)
Out[57]: u'c'

In [58]: unichr(68)
Out[58]: u'D'

12.ord(x)
ord()函数返回一个字符串参数的ASCII码或Unicode值。

In [60]: ord('a')
Out[60]: 97

In [61]: ord(u'A')
Out[61]: 65

13.hex(x)
hex()函数可把整数转换成十六进制数。

In [62]: hex(18)
Out[62]: '0x12'

In [63]: hex(121)
Out[63]: '0x79'

14.oct(x)
oct()函数可把给出的整数转换成八进制数。

In [64]: oct(8)
Out[64]: '010'

In [65]: oct(121)
Out[65]: '0171'

15.其他数据类型之间相互转换

In [76]: #Float转换为Long

In [77]: long(10.8)
Out[77]: 10L

In [78]: #Float转换为Int

In [79]: int(10.9)
Out[79]: 10

In [80]: #String转换为Int

In [82]: int('0xa',16)
Out[82]: 10

In [83]: int('1010',2)
Out[83]: 10

In [84]: #String转换为Long

In [85]: long('0xa',16)
Out[85]: 10L

In [86]: long('101010',2)
Out[86]: 42L

In [87]: #String转换为List

In [88]: name = 'nihao'

In [89]: list(name)
Out[89]: ['n', 'i', 'h', 'a', 'o']

In [90]: #Tuple转换为List

In [91]: atupl = ('this','is','a','book')

In [92]: list(atupl)
Out[92]: ['this', 'is', 'a', 'book']

In [93]: #String转换为Tuple

In [94]: str = "hello world"

In [95]: tuple(str)
Out[95]: ('h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd')

In [96]: #List转换为Tuple

In [97]: aa = ['nihao','zhongguo','shanghai']

In [98]: tuple(aa)
Out[98]: ('nihao', 'zhongguo', 'shanghai')

In [99]: #将List和Tuple复合数据类型转换为Dictionary

In [100]: atupl = ('this','is','a','book')

In [101]: aa = ['nihao','zhongguo','shanghai']

In [102]: zip(aa,atupl)
Out[102]: [('nihao', 'this'), ('zhongguo', 'is'), ('shanghai', 'a')]

In [103]: dict(zip(aa,atupl))
Out[103]: {'nihao': 'this', 'shanghai': 'a', 'zhongguo': 'is'}

In [104]: #Dictionary转换为List

In [105]: dic = {'name':'tom','age':26}

In [106]: dic.items()
Out[106]: [('age', 26), ('name', 'tom')]