Python __setattr__, __getattr__, __delattr__, __call__ usage examples _python

GetAttr

The ' getattr ' function belongs to the built-in function, and can be obtained by using the function name

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Value = Obj.attribute
Value = GetAttr (obj, "attribute")

Use ' getattr ' to implement Factory mode

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#一个模块支持html, text, XML and other formats of printing, according to the incoming formate parameters of different, call different functions to achieve the output of several formats

Import Statsout

def output (data, format= "text"):
Output_function = GetAttr (statsout, "output_%s"%format)
return Output_function (data)

__call__

The ' __call__ ' method is used for calls to the instance itself:

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Class Storage (DICT):
# __call__ method for invocation of instance itself
Effect of #达到 () call
def __call__ (self, key):
Try
return Self[key]
Except Keyerror, K:
Return None

s = Storage ()
s[' key ' = ' value '
Print S (key) #调用__call__

__getattr__

When you read a property from an object, you first need to search for the attribute from the self.__dicts__ and then look for it from the __getattr__.

Copy Code code as follows:

Class A (object):
def __init__ (self):
Self.name = ' from __dicts__: Zdy '

def __getattr__ (self, item):
If item = = ' Name ':
Return ' from __getattr__: Zdy '
elif item = = ' Age ':
Return 26

A = A ()
Print A.name # obtained from __dict__
Print A.age # obtained from __getattr__

__setattr__

The ' __setattr__ ' function is used to set the properties of an object, using the __SETATTR__ function in object to set the property:

Copy Code code as follows:

Class A (object):
def __setattr__ (self, *args, **kwargs):
print ' call func set attr '
Return object.__setattr__ (self, *args, **kwargs)

__delattr__

The ' __delattr__ ' function is used to delete an object's properties:

Copy Code code as follows:

Class A (object):
def __delattr__ (self, *args, **kwargs):
print ' Call func del attr '
Return object.__delattr__ (self, *args, **kwargs)

Example

Complete examples can refer to Weibo api:http://github.liaoxuefeng.com/sinaweibopy/

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Class _executable (object):

def __init__ (self, client, method, path):
self._client = Client
Self._method = method
Self._path = Path
#__call__函数实现_Executable函数对象为可调用的
def __call__ (self, **kw):
method = _method_map[self._method]
If Method==_http_post and ' pic ' in kw:
method = _http_upload
Return _http_call ('%s%s.json '% (Self._client.api_url, Self._path), method, Self._client.access_token, **kw)

def __str__ (self):
Return ' _executable (%s%s) '% (Self._method, Self._path)

__repr__ = __str__

Class _callable (object):

def __init__ (self, client, name):
self._client = Client
Self._name = Name

def __getattr__ (self, attr):
If attr== ' get ':
#初始化_Executable对象, call the __init__ function
Return _executable (self._client, ' get ', self._name)
If attr== ' post ':
Return _executable (self._client, ' POST ', self._name)
name = '%s/%s '% (Self._name, attr)
Return _callable (self._client, name)

def __str__ (self):
Return ' _callable (%s) '% Self._name

__repr__ = __str__

In the source code, there are the following snippets:

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Class Apiclient (object):
'''
API client using synchronized invocation.
'''
...

def __getattr__ (self, attr):
If ' __ ' in attr:
Return GetAttr (Self.get, attr)
Return _callable (self, attr)

So, join us to initialize the object and call a function as follows:

Copy Code code as follows:

Client = Apiclient (...)
#会调用__getattr__函数, thus calling the __call__ function
Client.something.get ()