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一、
property
属性高级用法
可以将对象方法作为属性使用
例子:
class
Foo:
def
__init__(
self
, age):
)
self
.__age
=
age
@
property
def
age(
self
):
return
self
.__age
@age.setter
def
age(
self
, args):
self
.__age
=
args
@age.deleter
def
age(
self
):
del
self
.__age
obj
=
Foo(
20
)
print
(obj.age)
obj.age
=
3
print
(obj.age)
del
obj.age
print
(obj.age)
class
Foo:
def
__init__(
self
, age):
self
.__age
=
age
def
get_age(
self
):
return
self
.__age
def
set_age(
self
, args):
self
.__age
=
args
def
del_age(
self
):
del
self
.__age
age
=
property
(get_age, set_age, del_age)
obj
=
Foo(
20
)
print
(obj.age)
obj.age
=
3
print
(obj.age)
del
obj.age
print
(obj.age)
__str__方法，默认返回对象内存地址，可以修改重写默认方法
例子:
class
Foo:
def
__init__(
self
, name, age):
self
.name
=
name
self
.age
=
age
def
__str__(
self
):
return
'name: %s, age: %s'
%
(
self
.name,
self
.age)
obj
=
Foo(
'egon'
,
'18'
)
print
(obj)
__getitem__, __setitem__,__delitem__可以通过字典的方式调用属性和方法
例子:
class
Foo:
def
__init__(
self
, name):
self
.name
=
name
def
__getitem__(
self
, item):
print
(
"getitem"
)
return
self
.__dict__[item]
def
__setitem__(
self
, key, value):
print
(
"setitem"
, key, value)
self
.__dict__[key]
=
value
def
__delitem__(
self
, key):
print
(
'del obj[key]时，执行'
)
self
.__dict__.pop(key)
obj
=
Foo(
'egon'
)
print
(obj.name)
#obj.name = 'alex'
#obj['name'] = 'alex'
print
(obj[
'name'
])
del
obj[
'name'
]
print
(obj[
'name'
])
__call__回掉函数，可以将对象变成可调用的
例子:
class
Foo:
def
__call__(
self
,
*
args,
*
*
kwargs):
print
(
'====>'
)
obj
=
Foo()
obj()
__getattr__
从对象中读取某个属性时，首先需要从
self
.__dicts__中搜索该属性，再从__getattr__中查找
__setattr__用来设置对象的属性，通过
object
中的__setattr__函数来设置属性
__delattr__用来删除对象的属性
例子:
class
Foo:
def
__init__(
self
, x):
self
.x
=
x
def
__getattr__(
self
, item):
print
(
'getattr'
)
def
__setattr__(
self
, key, value):
self
.__dict__[key]
=
value
def
__delattr__(
self
, item):
self
.__dict__.pop(item)
obj
=
Foo(
10
)
obj.x
=
1
print
(obj.__dict__)
del
obj.x
print
(obj.__dict__)
obj.a
=
1
obj.b
=
2
print
(obj.__dict__)
del
obj.a
print
(obj.__dict__)
print
(obj.aaaaaaaaa
exec
函数，将字符串中的python代码提取出来执行
例子:
s
=
"print(x)"
g
=
{
'x'
:
100000000
}
l
=
{
'x'
:
1
}
exec
(s,g,l)
s
=
"y=2"
exec
(s, g, l)
print
(g)
print
(l)
|
二、二次加工标准类
例子:
(): (itemtag=): ().(item) .tag=tag (p_object): (p_object): (%p_object) (List).append(p_object) (): mid_index=()//[mid_index] (): .tag: () ().clear() .tag=l=List([]) (l) (l.mid)
|
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实现迭代器协议
例子:
class
Foo:
def
__init__(
self
, n, stop):
self
.n
=
n
self
.stop
=
stop
def
__next__(
self
):
if
self
.n >
self
.stop:
raise
StopIteration
x
=
self
.n
self
.n
+
=
1
return
x
def
__iter__(
self
):
return
self
obj
=
Foo(
0
,
5
)
print
(
next
(obj))
print
(
next
(obj))
print
(
next
(obj))
实现上下文管理器:
例子:
class
Foo:
def
__init__(
self
, name):
self
.name
=
name
def
__enter__(
self
):
print
(
'enter'
)
return
self
def
__exit__(
self
, exc_type, exc_val, exc_tb):
print
(
'exit'
)
with Foo(
'alex'
) as x:
print
(x)
print
(
'=>'
)
print
(
'=>'
)
print
(
'=>'
)
|
本文转自小白的希望 51CTO博客，原文链接：http://blog.51cto.com/haoyonghui/1939924，如需转载请自行联系原作者
