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List: python-list
Subject: RE: built-in 'property'
From: Bob.Cowdery () CGI-Europe ! com
Date: 2004-12-28 21:53:35
Message-ID: 9B40DB5FBF7D2048AD79C2A91F862A51773208 () STEVAPPS05 ! Stevenage ! CGI-Europe ! com
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Thanks to everyone that has helped on this. What I am trying to do is create
a capability based api that I can build to order. This is as far as I get at
the moment.
Each of the first three classes represents some function I can do to a
radio, there would be many of these in practice. The next class is the API.
I figure I have to include all the possible radio function classes in this
as I can't figure out how to make the classes I include per instance. When I
create the API object I pass in a capability array as in the last class. I
use these classes as follows.
>>> import capability as c
>>> import radioapi as r
>>> caps = c.Capability()
>>> cap = caps.getCaps('SDR1000')
>>> cap
['mode', 'freq', 'blanker']
>>> api = r.API(cap)
>>> r.caps
['mode', 'freq', 'blanker']
>>> api.mode
Retrieving mode var "mode"
'lsb'
>>> api.freq
Retrieving freq var "freq"
7.0800000000000001
>>> api.blanker
Retrieving blanker var "blanker"
1
>>> hasattr(api, 'monitor')
0
This is the behaviour I want, each class responds if it is in the capability
array. The user can test attributes with hasattr(klass, 'att') to see if it
is supported. I can create another instance with a different radio and it
will respond accordingly. The problem of course is that in class API, caps
is global so as soon as I create another instance the first starts
responding to the new capability. If I try to make caps per instance I get
into all sorts of trouble with recursion. Does anyone have an idea how to
fix this or is it just impossible to make this work.
Regards
Bob
class Mode(object):
def __init__(self, initval=None, name='var'):
self.val = initval
self.name = name
def __get__(self, obj, objtype):
print 'Retrieving mode', self.name
return self.val
def __set__(self, obj, val):
print 'Updating mode' , self.name
self.val = val
import capability
class Freq(object):
def __init__(self, initval=None, name='var'):
self.val = initval
self.name = name
def __get__(self, obj, objtype):
print 'Retrieving freq', self.name
return self.val
def __set__(self, obj, val):
print 'Updating freq' , self.name
self.val = val
class Blanker(object):
def __init__(self, initval=None, name='var'):
self.val = initval
self.name = name
def __get__(self, obj, objtype):
print 'Retrieving blanker', self.name
return self.val
def __set__(self, obj, val):
print 'Updating blanker' , self.name
self.val = val
class API(object):
# create all possible radio classes
mode=Mode('lsb', 'var "mode"')
freq=Freq(7.080, 'var "freq"')
blanker=Blanker(True, 'var "blanker"')
global caps
caps = []
def __init__(self, pcaps):
global caps
caps = pcaps
def __getattribute__(self, key):
global caps
if (key in caps) or (key == 'caps'):
obj = object.__getattribute__(self, key)
if hasattr(obj, "__get__"):
return obj.__get__()
return obj
else:
raise AttributeError, "unreadable attribute"
class Capability(object):
m_cap = {
'SDR1000': ['mode','freq','blanker'],
'MyRig': ['mode','freq'],
'YourRig': ['mode', 'blanker']
}
def getCaps(self, radio):
return self.m_cap[radio]
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<META NAME="Generator" CONTENT="MS Exchange Server version 5.5.2653.12">
<TITLE>RE: built-in 'property'</TITLE>
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<BODY>
<P><FONT SIZE=2>Thanks to everyone that has helped on this. What I am trying to do is \
create a capability based api that I can build to order. This is as far as I get at \
the moment.</FONT></P>
<P><FONT SIZE=2>Each of the first three classes represents some function I can do to \
a radio, there would be many of these in practice. The next class is the API. I \
figure I have to include all the possible radio function classes in this as I can't \
figure out how to make the classes I include per instance. When I create the API \
object I pass in a capability array as in the last class. I use these classes as \
follows.</FONT></P>
<P><FONT SIZE=2>>>> import capability as c</FONT>
<BR><FONT SIZE=2>>>> import radioapi as r</FONT>
<BR><FONT SIZE=2>>>> caps = c.Capability()</FONT>
<BR><FONT SIZE=2>>>> cap = caps.getCaps('SDR1000')</FONT>
<BR><FONT SIZE=2>>>> cap</FONT>
<BR><FONT SIZE=2>['mode', 'freq', 'blanker']</FONT>
<BR><FONT SIZE=2>>>> api = r.API(cap)</FONT>
<BR><FONT SIZE=2>>>> r.caps</FONT>
<BR><FONT SIZE=2>['mode', 'freq', 'blanker']</FONT>
<BR><FONT SIZE=2>>>> api.mode</FONT>
<BR><FONT SIZE=2>Retrieving mode var "mode"</FONT>
<BR><FONT SIZE=2>'lsb'</FONT>
<BR><FONT SIZE=2>>>> api.freq</FONT>
<BR><FONT SIZE=2>Retrieving freq var "freq"</FONT>
<BR><FONT SIZE=2>7.0800000000000001</FONT>
<BR><FONT SIZE=2>>>> api.blanker</FONT>
<BR><FONT SIZE=2>Retrieving blanker var "blanker"</FONT>
<BR><FONT SIZE=2>1</FONT>
<BR><FONT SIZE=2>>>> hasattr(api, 'monitor')</FONT>
<BR><FONT SIZE=2>0</FONT>
</P>
<P><FONT SIZE=2>This is the behaviour I want, each class responds if it is in the \
capability array. The user can test attributes with hasattr(klass, 'att') to see if \
it is supported. I can create another instance with a different radio and it will \
respond accordingly. The problem of course is that in class API, caps is global so as \
soon as I create another instance the first starts responding to the new capability. \
If I try to make caps per instance I get into all sorts of trouble with recursion. \
Does anyone have an idea how to fix this or is it just impossible to make this \
work.</FONT></P>
<P><FONT SIZE=2>Regards</FONT>
<BR><FONT SIZE=2>Bob</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>class Mode(object):</FONT>
</P>
<P><FONT SIZE=2> def __init__(self, initval=None, \
name='var'):</FONT> <BR><FONT SIZE=2> \
self.val = initval</FONT> <BR><FONT SIZE=2> \
self.name = name</FONT> </P>
<P><FONT SIZE=2> def __get__(self, obj, objtype):</FONT>
<BR><FONT SIZE=2> print 'Retrieving mode', \
self.name</FONT> <BR><FONT SIZE=2> return \
self.val</FONT> </P>
<P><FONT SIZE=2> def __set__(self, obj, val):</FONT>
<BR><FONT SIZE=2> print 'Updating mode' , \
self.name</FONT> <BR><FONT SIZE=2> self.val \
= val</FONT> <BR><FONT SIZE=2>import capability</FONT>
</P>
<P><FONT SIZE=2>class Freq(object):</FONT>
</P>
<P><FONT SIZE=2> def __init__(self, initval=None, \
name='var'):</FONT> <BR><FONT SIZE=2> \
self.val = initval</FONT> <BR><FONT SIZE=2> \
self.name = name</FONT> </P>
<P><FONT SIZE=2> def __get__(self, obj, objtype):</FONT>
<BR><FONT SIZE=2> print 'Retrieving freq', \
self.name</FONT> <BR><FONT SIZE=2> return \
self.val</FONT> </P>
<P><FONT SIZE=2> def __set__(self, obj, val):</FONT>
<BR><FONT SIZE=2> print 'Updating freq' , \
self.name</FONT> <BR><FONT SIZE=2> self.val \
= val</FONT> <BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2>class Blanker(object):</FONT>
</P>
<P><FONT SIZE=2> def __init__(self, initval=None, \
name='var'):</FONT> <BR><FONT SIZE=2> \
self.val = initval</FONT> <BR><FONT SIZE=2> \
self.name = name</FONT> </P>
<P><FONT SIZE=2> def __get__(self, obj, objtype):</FONT>
<BR><FONT SIZE=2> print 'Retrieving \
blanker', self.name</FONT> <BR><FONT \
SIZE=2> return self.val</FONT> </P>
<P><FONT SIZE=2> def __set__(self, obj, val):</FONT>
<BR><FONT SIZE=2> print 'Updating blanker' \
, self.name</FONT> <BR><FONT SIZE=2> \
self.val = val </FONT> </P>
<P><FONT SIZE=2>class API(object):</FONT>
<BR>
<BR><FONT SIZE=2> # create all possible radio classes</FONT>
<BR><FONT SIZE=2> mode=Mode('lsb', 'var "mode"')</FONT>
<BR><FONT SIZE=2> freq=Freq(7.080, 'var "freq"')</FONT>
<BR><FONT SIZE=2> blanker=Blanker(True, 'var \
"blanker"')</FONT> <BR><FONT SIZE=2> global caps</FONT>
<BR><FONT SIZE=2> caps = []</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2> def __init__(self, pcaps):</FONT>
<BR><FONT SIZE=2> global caps</FONT>
<BR><FONT SIZE=2> caps = pcaps </FONT>
</P>
<P><FONT SIZE=2> def __getattribute__(self, key):</FONT>
<BR><FONT SIZE=2> global caps</FONT>
<BR><FONT SIZE=2> if (key in caps) or (key \
== 'caps'):</FONT> <BR><FONT \
SIZE=2> obj = \
object.__getattribute__(self, key)</FONT> <BR><FONT \
SIZE=2> if \
hasattr(obj, "__get__"):</FONT> <BR><FONT \
SIZE=2> \
return obj.__get__()</FONT> <BR><FONT \
SIZE=2> return \
obj</FONT> <BR><FONT SIZE=2> else:</FONT>
<BR><FONT SIZE=2> \
raise AttributeError, "unreadable attribute"</FONT> </P>
<P><FONT SIZE=2>class Capability(object):</FONT>
<BR><FONT SIZE=2> </FONT>
<BR><FONT SIZE=2> m_cap = {</FONT>
<BR><FONT SIZE=2> \
'SDR1000': ['mode','freq','blanker'],</FONT> <BR><FONT \
SIZE=2> 'MyRig': \
['mode','freq'],</FONT> <BR><FONT \
SIZE=2> 'YourRig': \
['mode', 'blanker']</FONT> <BR><FONT \
SIZE=2> }</FONT> \
<BR><FONT SIZE=2> </FONT> <BR><FONT SIZE=2> def \
getCaps(self, radio):</FONT> <BR><FONT \
SIZE=2> return self.m_cap[radio]</FONT> \
</P>
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