Python中常见工厂函数用法详解

>>> a=int(9.9)
>>> a
9
>>> b=long(45)
>>> b
45L
>>> f=float(8)
>>> f
8.0
>>> c=complex(8)
>>> c
(8+0j)
>>> b1=bool(7.9)
>>> b1
True
>>> b2=bool(0.0)
>>> b2
False
>>> b3=bool([])
>>> b2
False
>>> b4=bool((34,5))
>>> b4
True

>>> s=str(9.9)
>>> s
'9.9'
>>> unicode(9.0)
u'9.0'
>>> unicode('love')
u'love'

>>> l=list('python')
>>> l
['p', 'y', 't', 'h', 'o', 'n']
>>> t=tuple('python')
>>> t
('p', 'y', 't', 'h', 'o', 'n')

>>> type(6)
<type 'int'>
>>> type('python')
<type 'str'>
>>> type(u'love')
<type 'unicode'>
>>> class A():
...   pass
...
>>> a=A()
>>> type(a)
<type 'instance'>
>>> type(A)
<type 'classobj'>

>>> dict()
{}
>>> dict(one=1,two=2)
{'two': 2, 'one': 1}
>>> dict(zip(('one','two'),(1,2)))
{'two': 2, 'one': 1}
>>> dict([('one',1),('two',2)])
{'two': 2, 'one': 1}
>>> dict([['one',1],['two',2]])
{'two': 2, 'one': 1}
>>> dict((('one',1),('two',2)))
{'two': 2, 'one': 1}
>>> dict((['one',1],['two',2]))
{'two': 2, 'one': 1}

>>> s=set('python')
>>> s
set(['h', 'o', 'n', 'p', 't', 'y'])
>>> s.add(825)#可变集合
>>> s
set(['h', 'o', 'n', 'p', 't', 'y', 825])

>>> s=frozenset('python')
>>> s
frozenset(['h', 'o', 'n', 'p', 't', 'y'])
>>> s.add()#不可变集合
AttributeError: 'frozenset' object has no attribute 'add'