Am 15.02.2013 19:03, schrieb Dave Angel:
On 02/15/2013 12:23 PM, Bob Brusa wrote:
Am 15.02.2013 18:11, schrieb Dave Angel:
On 02/15/2013 11:59 AM, Bob Brusa wrote:
Hi,
I use a module downloaded from the net. Now I want to build my own
class, based
on the class SerialInstrument offered in this module - and in my class
I would
like to initialize a few things, using e. g. the method clear()
offered by
SerialInstrument. Hence I type:
class myClass(SerialInstrument)
self.clear(self)
def f1(self, str1, str2)
...do something etc.
I then get the message "self not know" from the statement
self.clear(self). I
have tried many other notations - none worked. What works is however
the
following code - specifying myClass without the self.clear(self) in it:
x = myClass("argument")
x.clear()
How can I integrate this call into the definition of myClass? Thanks
for advice.
Bob
By initialize, I'll assume you want this code to execute when your class
is instantiated. The way to do that is with a method called __init__().
Notice the double underscore at begin and end.
class myClass(SerialInstrument):
def __init__(self):
self.val1 = 42
self.val2 = 31
#... also initialize the base class
self.clear()
def f1(self, str1, str2):
....
You should also call the __init__() method of the base class. But I
don't know whether you're using Python2 or Python3, so I won't write
that call
This is without knowing anything about your base class, so there may be
many other adjustments to be made.
I defined (which should clear visa-buffers when instantiating the class):
class myvisa(visa.SerialInstrument):
def __init__ (self):
self.clear()
I still don't see the call to the superclass __init__(). Get that code
from Bob Brusa's message.
def io (self, printstr, askstr):
...cut
when I run (python 2.7) a program using this class I get this:
C:\Projekte\TDSsw\mypython>python chk_clear_1.py
Traceback (most recent call last):
File "chk_clear_1.py", line 8, in <module>
from myvisa import *
File "C:\Projekte\TDSsw\mypython\myvisa.py", line 15, in <module>
class myvisa(visa.SerialInstrument):
File "C:\Projekte\TDSsw\mypython\myvisa.py", line 121, in myvisa
visa.Instrument.clear()
TypeError: unbound method clear() must be called with Instrument
instance as first argument (got nothing instead)
would it help to define instead:
class myvisa(visa.SerialInstrument):
def __init__ (self):
x = SerialInstrument(self)
x.clear() #and then forget about this x?
def io (self, printstr, askstr):
...cut
Besides being indented wrong (did you even try it ?), that code doesn't
begin to be what you want. You're calling clear on some other instance,
then throwing that instance away, and not clearing the one you just
created.
But as I said before, you haven't said word-one about what the base
class looks like, or how it's supposed to be used, nor when clear() is
supposed to be called.
You also aren't showing us the code which got the error, so I can't see
how we could help. What does the code around line 115 look like? Is it
part of the same class definition?
Dave,
to make it more clear, I attach a cut-down version of my program. It
includes comments to explain in more detail what my problem is.
Bob
"""/
edit history:
15-02-2013 Creation
"""
import sys
import visa
import time
class myvisa(visa.SerialInstrument):
"""provide utilities to handle the instrument
"""
# def __init__ (): this doe not work
# self.clear()
def io (self, printstr, askstr):
"""combines a print and an ask-string into a single call
"""
res = 0
try:
antw = self.ask(askstr)
except:
antw = "time-out"
res = 1
print printstr + antw
return res
strich = " | "; pfeil = "->"
print "start of program q1.py"
iodev = "COM9"
tds = myvisa(iodev, baud_rate = 57600)
tds.clear() # this call I want to be called automatically when instantiating
the class
cmd = "*idn?"; tds.io(pfeil+cmd+strich,cmd)
cmd = "status?"; tds.write(cmd) # exit with something in the visa-buffer
and this will
# lead to a de-chronization between write
and reads when
# executing a next program
print "end of program"
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