I'm obviously doing something very silly here but at the moment I
can't see what.

Here's the code:-

#!/usr/bin/python3
#
#
# GPIO
#
import gpiod
#
#
# Simple wrapper class for gpiod to make set and clearing outputs
easier
#
class Gpiopin:

def __init__(self, pin):
#
#
# scan through the GPIO chips to find the line/pin we want
#
for c in ['gpiochip0', 'gpiochip1', 'gpiochip2', 'gpiochip3']:

chip = gpiod.Chip(c)
for l in range(32):
line = chip.get_line(l)
if pin in line.name():
print("Found: ", line.name())
return
else:
raise ValueError("Can't find pin '" + pin + "'")

def print_name(self):
print (self.line.name())

def set(self):
self.line.set_value(1)

def clear(self):
self.line.set_value(0)


This is by no means the final code, the print() in the __init__() is
just a diagnostic for example. However I really can't understand why I
see the following when I try it:-

>>> import ngp
>>> ngp.Gpiopin("P9_23")
Found: P9_23
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/chris/.cfg/hosts/bbb/bin/ngp.py", line 24, in __init__
return
ValueError: Can't find pin 'P9_23'
>>>

Does a return in __init__() not do what I think it does?

How else could/should I do this?





--
Chris Green
·

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Chris Green <cl@isbd.net> wrote:

[snip code and question]

Sorry folks, it was a caching problem, I wasn't running the code I
thought I was running! When I made sure I had cleared everything out
and tried again it all worked as I expected.

--
Chris Green
·

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Thu, Aug 31, 2023 at 3:19 PM Chris Green via Python-list <python-list@python.org> wrote:

I'm obviously doing something very silly here but at the moment I
can't see what.

Here's the code:-

#!/usr/bin/python3
#
#
# GPIO
#
import gpiod
#
#
# Simple wrapper class for gpiod to make set and clearing outputs
easier
#
class Gpiopin:

def __init__(self, pin):
#
#
# scan through the GPIO chips to find the line/pin we want
#
for c in ['gpiochip0', 'gpiochip1', 'gpiochip2', 'gpiochip3']:

chip = gpiod.Chip(c)
for l in range(32):
line = chip.get_line(l)
if pin in line.name():
print("Found: ", line.name())
return
else:
raise ValueError("Can't find pin '" + pin + "'")

def print_name(self):
print (self.line.name())

def set(self):
self.line.set_value(1)

def clear(self):
self.line.set_value(0)

This is by no means the final code, the print() in the __init__() is
just a diagnostic for example. However I really can't understand why I
see the following when I try it:-

>>> import ngp
>>> ngp.Gpiopin("P9_23")
Found: P9_23
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/chris/.cfg/hosts/bbb/bin/ngp.py", line 24, in __init__
return
ValueError: Can't find pin 'P9_23'
>>>

Does a return in __init__() not do what I think it does?

How else could/should I do this?

Change the return to a break

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 31/08/2023 22:15, Chris Green via Python-list wrote:

class Gpiopin:

def __init__(self, pin):
#
#
# scan through the GPIO chips to find the line/pin we want
#
for c in ['gpiochip0', 'gpiochip1', 'gpiochip2', 'gpiochip3']:

chip = gpiod.Chip(c)
for l in range(32):
line = chip.get_line(l)
if pin in line.name():
print("Found: ", line.name())
return
else:
raise ValueError("Can't find pin '" + pin + "'")

You don't store the line anywhere.
You need to use self.line
self.line = chip.get_line(l)
if pin...

def print_name(self):
print (self.line.name())

def set(self):
self.line.set_value(1)

def clear(self):
self.line.set_value(0)

As you do here.

--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Alan Gauld <learn2program@gmail.com> wrote:

On 31/08/2023 22:15, Chris Green via Python-list wrote:

class Gpiopin:

def __init__(self, pin):
#
#
# scan through the GPIO chips to find the line/pin we want
#
for c in ['gpiochip0', 'gpiochip1', 'gpiochip2', 'gpiochip3']:

chip = gpiod.Chip(c)
for l in range(32):
line = chip.get_line(l)
if pin in line.name():
print("Found: ", line.name())
return
else:
raise ValueError("Can't find pin '" + pin + "'")

You don't store the line anywhere.
You need to use self.line
self.line = chip.get_line(l)
if pin...

def print_name(self):
print (self.line.name())

def set(self):
self.line.set_value(1)

def clear(self):
self.line.set_value(0)

As you do here.

Yes, OK, absolutely. However that wasn't my original rather basic
problem which was, as I said, that I wasn't running the code I was
looking at.

The above was just a quick hack from some even cruder code doing the
same job, trying to develop it into something better and more general.

It's all on a headless Beaglebone Black (bit like a Raspberry Pi) so
I'm doing everything via multiple ssh connections and sometimes this
results in "the left hand not knowing what the right hand is doing"!

--
Chris Green
·

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Chris Green <cl@isbd.net> writes:

I'm obviously doing something very silly here but at the
moment I can't see what.

not adding debug print statements to see what exactly happens

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)