python 数据类型转换教案_Python 数据类型转换

sys.maxint

>>> import sys

>>> print sys.maxint

9223372036854775807

字符串转换成整数

int(s,[base])

将字符串转换成整数，如果指定转换进制，则把字符串按指定进制转换成十进制数。如果字符串不是一个有效的数值则会触发ValueError 异常

>>> int('1001',2)

9

>>> int('FF', 16)

255

>>> int('23', 8)

19

>>> int('12', 5)

7

当字符串无法转换成数字时

>>> int('anfs', 10)

Traceback (most recent call last):

File "", line 1, in

ValueError: invalid literal for int() with base 10: 'anfs'

字符串转浮点数

float(s)

根据字符串返回一个浮点数，如果不是一个有效的字符串，则会触发ValueError异常

>>> e = float('3.14159')

>>> e

3.14159

>>> type(e)

数值类型转字符串

str(X)

返回一个基于X数值的字符串，如果数值无效，则会触发异常

>>> str(3.14149)

'3.14149'

>>> str(123456)

'123456'

>>> str(add)

Traceback (most recent call last):

File "", line 1, in

NameError: name 'add' is not defined

>>> str(123L)

'123'

>>>

列表或字符串转元组

tuple(s)

返回基于序列s的一个元组，s可以为列表或字符串，否则触发异常

>>> tuple([1, 3, 5])

(1, 3, 5)

>>> tuple('Hello World')

('H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd')

>>> tuple(123)

Traceback (most recent call last):

File "", line 1, in

TypeError: 'int' object is not iterable

>>>

元组或字符串转列表

list(s)

返回基于序列s的一个列表，s可以为元组或字符串，否则触发异常

>>> list((1, 2, 3))

[1, 2, 3]

>>> list('Hello')

['H', 'e', 'l', 'l', 'o']

>>> list(abc)

Traceback (most recent call last):

File "", line 1, in

NameError: name 'abc' is not defined

>>> list(123)

Traceback (most recent call last):

File "", line 1, in

TypeError: 'int' object is not iterable

到集合的转换

set(l)

返回一个基于序列l的集合，l可以为列表，元组或字符串

>>> set([11, 3, 7])

set([3, 11, 7])

>>> set((11, 3, 7))

set([3, 11, 7])

>>> set('Hello')

set(['H', 'e', 'l', 'o'])

>>> set(123)

Traceback (most recent call last):

File "", line 1, in

TypeError: 'int' object is not iterable

到字典的转换

dict(s)

s必须是以键值对的形式组合的列表或元组

>>> dict([('name', 'xiao'), ('age', 28)])

{'age': 28, 'name': 'xiao'}

>>> dict((('name', 'xiao'), ('age', 28)))

{'age': 28, 'name': 'xiao'}

>>> dict((['name', 'xiao'], ['age', 28]))

{'age': 28, 'name': 'xiao'}

>>> dict('age', 28)

Traceback (most recent call last):

File "", line 1, in

TypeError: dict expected at most 1 arguments, got 2

>>> dict(['age', 28])

Traceback (most recent call last):

File "", line 1, in

ValueError: dictionary update sequence element #0 has length 3; 2 is required

>>> dict([('age', 28)])

{'age': 28}

>>> dict((('age', 28)))

Traceback (most recent call last):

File "", line 1, in

ValueError: dictionary update sequence element #0 has length 3; 2 is required

>>> dict([['age', 28]])

{'age': 28}

到frozenset的转换

frozenset(s)

>>> s = set([1, 2, 3])

>>> frozenset(s)

frozenset([1, 2, 3])

>>> frozenset([1, 2, 3])

frozenset([1, 2, 3])

>>> frozenset((1, 2, 3))

frozenset([1, 2, 3])

>>> frozenset('hello')

frozenset(['h', 'e', 'l', 'o'])

数字转字符

chr(x)

从整数x返回一个字符，x的取值范围是 0 ~ 255

>>> chr(0)

'\x00'

>>> chr(65)

'A'

>>> chr(255)

'\xff'

>>> chr(-1)

Traceback (most recent call last):

File "", line 1, in

ValueError: chr() arg not in range(256)

>>> chr(256)

Traceback (most recent call last):

File "", line 1, in

ValueError: chr() arg not in range(256)

数字转unicode字符

unichr(x)

从整数返回一个unicode字符， x的取值范围在大多数系统上为 0 到65536

>>> unichr(1000)

u'\u03e8'

>>> unichr(65)

u'A'

>>> unichr(-1)

Traceback (most recent call last):

File "", line 1, in

ValueError: unichr() arg not in range(0x110000) (wide Python build)

>>> unichr(65536)

u'\U00010000'

>>> unichr(65537)

u'\U00010001'

返回一个字符的ASCII码

ord(c)

>>> ord('a')

97

从整数返回一个十六进制字符串

hex(x)

>>> hex(121)

'0x79'

从整数返回一个八进制字符串

oct(x)

>>> oct(121)

'0171'

从整数返回一个二进制字符串

bin(x)

>>> bin(878)

'0b1101101110'