Re: [Tutor] Need help with using methods in a base class

2008-09-08 Thread Roy Khristopher Bayot 
Hi. It worked.

 class LightsHandle(Parallel):
... def __init__(self):
... Parallel.__init__(self)
... def __del__(self):
... Parallel.__del__(self)
... def setLatch(self, x, y, z):
... self.setDataStrobe(x)
... print 'Data Strobe set. \n'
... self.setAutoFeed(y)
... print 'AutoFeed set. \n'
... self.setInitOut(z)
... print 'InitOut set. \n'
... def generateClockPulse(self):
... self.setSelect(0)
... print 'Select set to 0. \n'
... self.setSelect(1)
... print 'Select set to 1. \n'

Just to answer some questions.

Is _fd initialized in Parallel.__init__() ?

Yes it is.

 I already tried using the base class and it works just fine.

 from parallel import Parallel
 p = Parallel()
 p.setData(0xFF)

Note this is a different value than you used above, is that significant?

No, not really. It's just what I want to output. 0xFF would mean all 8 LEDs
are off while 0xF0 would mean only half the lights are on.

Thank you very much.


On Mon, Sep 8, 2008 at 2:35 AM, Kent Johnson [EMAIL PROTECTED] wrote:

 On Sun, Sep 7, 2008 at 11:07 AM, Roy Khristopher Bayot
 [EMAIL PROTECTED] wrote:
  Hi. I added self to parts of the code. But after making an instance and
  using the setData method it gave out an AttributeError.
 
  from parallel import Parallel
  class LightsHandle(Parallel):
  ... def __init__(self):
  ... pass

 This will *prevent* Parallel.__init__() from being called. I guess
 this is not what you want, it is probably the cause of your trouble.
 Is _fd initialized in Parallel.__init__() ?

  ... def setData(self, data):
  ... Parallel.setData(self, data)

 This method is not needed at all. If you omit it, the base class
 method will be called automatically when you call setData() on a
 LightsHandle instance.

  ... def setLatch(self, latch):
  ... Parallel.setDataStrobe(self, int(latch[0]))
  ... Parallel.setAutoFeed(self, int(latch[1]))
  ... Parallel.setInitOut(self, int(latch[2]))

 This could be written more simply and idiomatically as

 ... def setLatch(self, x, y, z):
 ... self.setDataStrobe(x)
 ... self.setAutoFeed(y)
 ... self.setInitOut(z)

 Since you have not overridden these methods you can call them directly.

  ... def generateClockPulse(self):
  ... Parallel.setSelect(self, 0)
  ... Parallel.setSelect(self, 1)

 Same here.

  a = LightsHandle()
  a.setData(0xF0)
  Traceback (most recent call last):
File stdin, line 1, in module
File stdin, line 5, in setData
File /usr/lib/python2.5/site-packages/parallel/parallelppdev.py, line
  563, in setData
  return self.PPWDATA(d)
File /usr/lib/python2.5/site-packages/parallel/parallelppdev.py, line
  465, in PPWDATA
  fcntl.ioctl(self._fd, PPWDATA,struct.pack('B',byte))
  AttributeError: LightsHandle instance has no attribute '_fd'
 
  Does this mean I have to make '_fd' in class LightsHandle? I thought that
 it
  would be somewhat messy. And there might be other variables that werent
  accounted for.

 Probably it means you have to call the base class __init__().

  a = LightsHandle()
  a.setData(0xF0)
 
  There were no errors thrown. But the problem is that it doesnt work.

  I already tried using the base class and it works just fine.
 
  from parallel import Parallel
  p = Parallel()
  p.setData(0xFF)

 Note this is a different value than you used above, is that significant?

 Kent

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Re: [Tutor] Need help with using methods in a base class

2008-09-08 Thread Kent Johnson 
On Mon, Sep 8, 2008 at 9:21 AM, Roy Khristopher Bayot
[EMAIL PROTECTED] wrote:
 Hi. It worked.

:-)

 class LightsHandle(Parallel):
 ... def __init__(self):
 ... Parallel.__init__(self)
 ... def __del__(self):
 ... Parallel.__del__(self)

These two methods are not needed. If you omit them, the base class
methods will be called by default. You only need a subclass __init__()
method if it is doing initialization specific to the subclass.

It is very rare to define a __del__() method at all.

Kent
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Re: [Tutor] Need help with using methods in a base class

2008-09-07 Thread Roy Khristopher Bayot 
Hi. I added self to parts of the code. But after making an instance and
using the setData method it gave out an AttributeError.

 from parallel import Parallel
 class LightsHandle(Parallel):
... def __init__(self):
... pass
... def setData(self, data):
... Parallel.setData(self, data)
... def setLatch(self, latch):
... Parallel.setDataStrobe(self, int(latch[0]))
... Parallel.setAutoFeed(self, int(latch[1]))
... Parallel.setInitOut(self, int(latch[2]))
... def generateClockPulse(self):
... Parallel.setSelect(self, 0)
... Parallel.setSelect(self, 1)
...
 a = LightsHandle()
 a.setData(0xF0)
Traceback (most recent call last):
  File stdin, line 1, in module
  File stdin, line 5, in setData
  File /usr/lib/python2.5/site-packages/parallel/parallelppdev.py, line
563, in setData
return self.PPWDATA(d)
  File /usr/lib/python2.5/site-packages/parallel/parallelppdev.py, line
465, in PPWDATA
fcntl.ioctl(self._fd, PPWDATA,struct.pack('B',byte))
AttributeError: LightsHandle instance has no attribute '_fd'

Does this mean I have to make '_fd' in class LightsHandle? I thought that it
would be somewhat messy. And there might be other variables that werent
accounted for.

So I did something else.

 class LightsHandle(Parallel):
... def __init__(self):
... Parallel.__init__(self, port = 0)
... def __del__(self):
... Parallel.__del__(self)
... def setData(self, data):
... Parallel.setData(self, data)
... def setLatch(self, latch):
... Parallel.setDataStrobe(self, int(latch[0]))
... Parallel.setAutoFeed(self, int(latch[1]))
... Parallel.setInitOut(self, int(latch[2]))
... def generateClockPulse(self):
... Parallel.setSelect(self,0)
... Parallel.setSelect(self,1)
...
 a = LightsHandle()
 a.setData(0xF0)
 a.setLatch('111')
 a.generateClockPulse()
 a.setLatch('110')
 a.generateClockPulse()
 a.setData(0x0F)
 a.setLatch('111')
 a.generateClockPulse()

There were no errors thrown. But the problem is that it doesnt work. This
was suppose to control 32 LEDs (8 LEDs per latch, 6 latches total). Method
setData() is suppose to control the 8 bits that you want to output on a
specific latch. Method setLatch() will specify the latch. Method
generateClockPulse() will cause the specific latch to take in the data and
retain it there.

But it doesnt work. The LEDs couldnt be controlled.

I already tried using the base class and it works just fine.

 from parallel import Parallel
 p = Parallel()
 p.setData(0xFF)
 p.setDataStrobe(1)
 p.setAutoFeed(1)
 p.setInitOut(1)
 p.setSelect(0)
 p.setSelect(1)

So I thought maybe there was something wrong with setLatch() since elements
of the string were converted to integers. I changed the code again.

 class LightsHandle(Parallel):
... def __init__(self):
... Parallel.__init__(self, port = 0)
... def __del__(self):
... Parallel.__del__(self)
... def setData(self, data):
... Parallel.setData(self, data)
... def setLatch(self, x, y, z):
... Parallel.setDataStrobe(self, x)
... Parallel.setAutoFeed(self, y)
... Parallel.setInitOut(self, z)
... def generateClockPulse(self):
... Parallel.setSelect(self,0)
... Parallel.setSelect(self,1)
...
 a = LightsHandle()
 a.setData(0xF0)
 a.setLatch(1,1,1)
 a.generateClockPulse()
 a.setData(0x0F)
 a.setLatch(1,1,1)
 a.generateClockPulse()

But no LED lights were changing as it was suppose to.

Any ideas on what I dont know or what I've overlooked?


On Sun, Sep 7, 2008 at 6:07 AM, Alan Gauld [EMAIL PROTECTED]wrote:

 Roy Khristopher Bayot [EMAIL PROTECTED] wrote


  ... def generateClockPulse(self):
 ... parallel.Parallel.setSelect(0)
 ... parallel.Parallel.setSelect(1)
 ...

 a = LightsHandle()
 a.setD(0xF0)

 Traceback (most recent call last):
  File stdin, line 1, in module
  File stdin, line 5, in setD
 TypeError: unbound method setData() must be called with Parallel instance
 as
 first argument (got int instance instead)


 The error merssage gives the clue. Sonce you are calling a method
 on a classs not an object you need to pass in the instance reference
 explicitly. Its exactly as in calling the base constructor in __init__

 class C(P):
  def __init__(self):
 P.__init__(self)# need to pass self here

  (Some notes: I changed setData() to setD() so that there wont be a
 confusion. Method setData() is from the base class Parallel. Although I
 think setData() could be overriden.)


 Thats not necessary, each class creates its owen namespace.

  What have I been doing wrong? Why does it say that I need a Parallel
 instance?


 Because the class needs to know where to find the instance variables.
 Since you are calling the class directly, not via an instance you have
 to pass self explicitly.

Re: [Tutor] Need help with using methods in a base class

2008-09-07 Thread Kent Johnson 
On Sun, Sep 7, 2008 at 11:07 AM, Roy Khristopher Bayot
[EMAIL PROTECTED] wrote:
 Hi. I added self to parts of the code. But after making an instance and
 using the setData method it gave out an AttributeError.

 from parallel import Parallel
 class LightsHandle(Parallel):
 ... def __init__(self):
 ... pass

This will *prevent* Parallel.__init__() from being called. I guess
this is not what you want, it is probably the cause of your trouble.
Is _fd initialized in Parallel.__init__() ?

 ... def setData(self, data):
 ... Parallel.setData(self, data)

This method is not needed at all. If you omit it, the base class
method will be called automatically when you call setData() on a
LightsHandle instance.

 ... def setLatch(self, latch):
 ... Parallel.setDataStrobe(self, int(latch[0]))
 ... Parallel.setAutoFeed(self, int(latch[1]))
 ... Parallel.setInitOut(self, int(latch[2]))

This could be written more simply and idiomatically as

... def setLatch(self, x, y, z):
... self.setDataStrobe(x)
... self.setAutoFeed(y)
... self.setInitOut(z)

Since you have not overridden these methods you can call them directly.

 ... def generateClockPulse(self):
 ... Parallel.setSelect(self, 0)
 ... Parallel.setSelect(self, 1)

Same here.

 a = LightsHandle()
 a.setData(0xF0)
 Traceback (most recent call last):
   File stdin, line 1, in module
   File stdin, line 5, in setData
   File /usr/lib/python2.5/site-packages/parallel/parallelppdev.py, line
 563, in setData
 return self.PPWDATA(d)
   File /usr/lib/python2.5/site-packages/parallel/parallelppdev.py, line
 465, in PPWDATA
 fcntl.ioctl(self._fd, PPWDATA,struct.pack('B',byte))
 AttributeError: LightsHandle instance has no attribute '_fd'

 Does this mean I have to make '_fd' in class LightsHandle? I thought that it
 would be somewhat messy. And there might be other variables that werent
 accounted for.

Probably it means you have to call the base class __init__().

 a = LightsHandle()
 a.setData(0xF0)

 There were no errors thrown. But the problem is that it doesnt work.

 I already tried using the base class and it works just fine.

 from parallel import Parallel
 p = Parallel()
 p.setData(0xFF)

Note this is a different value than you used above, is that significant?

Kent
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Re: [Tutor] Need help with using methods in a base class

2008-09-06 Thread Kent Johnson 
On Sat, Sep 6, 2008 at 12:04 PM, Roy Khristopher Bayot
[EMAIL PROTECTED] wrote:
 Hi. I am having some difficulty using methods from a base class.

 I have 2 classes. The first one is Parallel which is inside the module
 parallel. The methods useful to me from this class are setDataStrobe(),
 setAutoFeed(), setInitOut(), setSelect(), and setData().

 The second one is derived from the first. I called it LightsHandle. The code
 and traceback is written below:

 import parallel
 class LightsHandle(parallel.Parallel):
 ... def __init__(self):
 ... pass
 ... def setData(self, data):
 ... Parallel.setData(data)
 ... def setLatch(self, latch):
 ... Parallel.setDataStrobe(int(latch[0]))
 ... Parallel.setAutoFeed(int(latch[1]))
 ... Parallel.setInitOut(int(latch[2]))
 ... def generateClockPulse(self):
 ... Parallel.setSelect(0)
 ... Parallel.setSelect(1)
 ...
 a = LightsHandle()
 a.setData(0xF0)
 Traceback (most recent call last):
   File stdin, line 1, in module
   File stdin, line 5, in setData
 NameError: global name 'Parallel' is not defined

This error is because you did not import Parallel, you imported
parallel. You have to use the full name parallel.Parallel as you
figured out. You could also use
  from parallel import Parallel
and then just refer to Parallel.

 So I tried another one. And the code and traceback is written below.

 import parallel
 class LightsHandle(parallel.Parallel):
 ... def __init__(self):
 ... pass
 ... def setD(self, data):
 ... parallel.Parallel.setData(data)
 ... def setLatch(self, latch):
 ... parallel.Parallel.setDataStrobe(int(latch[0]))
 ... parallel.Parallel.setAutoFeed(int(latch[1]))
 ... parallel.Parallel.setInitOut(int(latch[2]))
 ... def generateClockPulse(self):
 ... parallel.Parallel.setSelect(0)
 ... parallel.Parallel.setSelect(1)
 ...
 a = LightsHandle()
 a.setD(0xF0)
 Traceback (most recent call last):
   File stdin, line 1, in module
   File stdin, line 5, in setD
 TypeError: unbound method setData() must be called with Parallel instance as
 first argument (got int instance instead)

 (Some notes: I changed setData() to setD() so that there wont be a
 confusion. Method setData() is from the base class Parallel. Although I
 think setData() could be overriden.)

 What have I been doing wrong? Why does it say that I need a Parallel
 instance?

 According to
 http://www.python.org/doc/2.5/tut/node11.html#SECTION001134

 There is a simple way to call the base class method directly: just call
 BaseClassName.methodname(self, arguments). This is occasionally useful to
 clients as well. (Note that this only works if the base class is defined or
 imported directly in the global scope.) 

This quote has the answer to your question. When you call the base
class method, you have to explicitly provide the self parameter, e.g.
  parallel.Parallel.setData(self, data)

Kent
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Re: [Tutor] Need help with using methods in a base class

2008-09-06 Thread Alan Gauld 

Roy Khristopher Bayot [EMAIL PROTECTED] wrote



... def generateClockPulse(self):
... parallel.Parallel.setSelect(0)
... parallel.Parallel.setSelect(1)
...

a = LightsHandle()
a.setD(0xF0)

Traceback (most recent call last):
 File stdin, line 1, in module
 File stdin, line 5, in setD
TypeError: unbound method setData() must be called with Parallel 
instance as

first argument (got int instance instead)


The error merssage gives the clue. Sonce you are calling a method
on a classs not an object you need to pass in the instance reference
explicitly. Its exactly as in calling the base constructor in __init__

class C(P):
  def __init__(self):
 P.__init__(self)# need to pass self here


(Some notes: I changed setData() to setD() so that there wont be a
confusion. Method setData() is from the base class Parallel. 
Although I

think setData() could be overriden.)


Thats not necessary, each class creates its owen namespace.


What have I been doing wrong? Why does it say that I need a Parallel
instance?


Because the class needs to know where to find the instance variables.
Since you are calling the class directly, not via an instance you have
to pass self explicitly.

Remember that in

class C:
  def m(self, x): print x

c = C(42)


Then c.m() is the same as C.m(c,42). self takes on the value of
the instance in the first case but in the second you have to pass
it directly. When you are inside a methiod you always use the
second form so you always need to pass self.

HTH,

--
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld 



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