mirror of
https://github.com/KevinMidboe/python-gpiozero.git
synced 2025-10-29 09:40:36 +00:00
c820636fcb
This implements the proposal discussed in the re-opened #279 to add a pin_factory argument at the device level and remove the ability to specify a pin instance to device constructors (they now only accept a pin specification). Note: there's still a couple of bits to tidy up (tests on "real" Pis, and pin_factory.release_all needs refinement) but the test suite is now at least capable of passing on a PC.
479 lines
18 KiB
Python
479 lines
18 KiB
Python
from __future__ import (
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unicode_literals,
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print_function,
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absolute_import,
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division,
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)
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nstr = str
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str = type('')
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import os
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import atexit
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import weakref
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import warnings
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from collections import namedtuple
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from itertools import chain
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from types import FunctionType
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from threading import Lock
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import pkg_resources
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from .pins import Pin
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from .threads import _threads_shutdown
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from .mixins import (
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ValuesMixin,
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SharedMixin,
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)
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from .exc import (
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BadPinFactory,
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DeviceClosed,
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CompositeDeviceBadName,
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CompositeDeviceBadOrder,
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CompositeDeviceBadDevice,
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GPIOPinMissing,
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GPIOPinInUse,
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GPIODeviceClosed,
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PinFactoryFallback,
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)
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from .compat import frozendict
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class GPIOMeta(type):
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# NOTE Yes, this is a metaclass. Don't be scared - it's a simple one.
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def __new__(mcls, name, bases, cls_dict):
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# Construct the class as normal
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cls = super(GPIOMeta, mcls).__new__(mcls, name, bases, cls_dict)
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# If there's a method in the class which has no docstring, search
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# the base classes recursively for a docstring to copy
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for attr_name, attr in cls_dict.items():
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if isinstance(attr, FunctionType) and not attr.__doc__:
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for base_cls in cls.__mro__:
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if hasattr(base_cls, attr_name):
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base_fn = getattr(base_cls, attr_name)
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if base_fn.__doc__:
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attr.__doc__ = base_fn.__doc__
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break
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return cls
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def __call__(cls, *args, **kwargs):
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# Make sure cls has GPIOBase somewhere in its ancestry (otherwise
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# setting __attrs__ below will be rather pointless)
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assert issubclass(cls, GPIOBase)
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if issubclass(cls, SharedMixin):
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# If SharedMixin appears in the class' ancestry, convert the
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# constructor arguments to a key and check whether an instance
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# already exists. Only construct the instance if the key's new.
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key = cls._shared_key(*args, **kwargs)
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try:
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self = cls._instances[key]
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self._refs += 1
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except (KeyError, ReferenceError) as e:
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self = super(GPIOMeta, cls).__call__(*args, **kwargs)
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self._refs = 1
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# Replace the close method with one that merely decrements
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# the refs counter and calls the original close method when
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# it reaches zero
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old_close = self.close
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def close():
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self._refs = max(0, self._refs - 1)
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if not self._refs:
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try:
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old_close()
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finally:
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try:
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del cls._instances[key]
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except KeyError:
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# If the _refs go negative (too many closes)
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# just ignore the resulting KeyError here -
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# it's already gone
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pass
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self.close = close
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cls._instances[key] = weakref.proxy(self)
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else:
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# Construct the instance as normal
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self = super(GPIOMeta, cls).__call__(*args, **kwargs)
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# At this point __new__ and __init__ have all been run. We now fix the
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# set of attributes on the class by dir'ing the instance and creating a
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# frozenset of the result called __attrs__ (which is queried by
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# GPIOBase.__setattr__). An exception is made for SharedMixin devices
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# which can be constructed multiple times, returning the same instance
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if not issubclass(cls, SharedMixin) or self._refs == 1:
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self.__attrs__ = frozenset(dir(self))
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return self
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# Cross-version compatible method of using a metaclass
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class GPIOBase(GPIOMeta(nstr('GPIOBase'), (), {})):
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def __setattr__(self, name, value):
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# This overridden __setattr__ simply ensures that additional attributes
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# cannot be set on the class after construction (it manages this in
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# conjunction with the meta-class above). Traditionally, this is
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# managed with __slots__; however, this doesn't work with Python's
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# multiple inheritance system which we need to use in order to avoid
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# repeating the "source" and "values" property code in myriad places
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if hasattr(self, '__attrs__') and name not in self.__attrs__:
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raise AttributeError(
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"'%s' object has no attribute '%s'" % (
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self.__class__.__name__, name))
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return super(GPIOBase, self).__setattr__(name, value)
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def __del__(self):
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self.close()
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def close(self):
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"""
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Shut down the device and release all associated resources. This method
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can be called on an already closed device without raising an exception.
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This method is primarily intended for interactive use at the command
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line. It disables the device and releases its pin(s) for use by another
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device.
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You can attempt to do this simply by deleting an object, but unless
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you've cleaned up all references to the object this may not work (even
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if you've cleaned up all references, there's still no guarantee the
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garbage collector will actually delete the object at that point). By
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contrast, the close method provides a means of ensuring that the object
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is shut down.
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For example, if you have a breadboard with a buzzer connected to pin
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16, but then wish to attach an LED instead:
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>>> from gpiozero import *
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>>> bz = Buzzer(16)
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>>> bz.on()
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>>> bz.off()
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>>> bz.close()
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>>> led = LED(16)
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>>> led.blink()
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:class:`Device` descendents can also be used as context managers using
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the :keyword:`with` statement. For example:
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>>> from gpiozero import *
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>>> with Buzzer(16) as bz:
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... bz.on()
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...
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>>> with LED(16) as led:
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... led.on()
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...
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"""
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# This is a placeholder which is simply here to ensure close() can be
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# safely called from subclasses without worrying whether super-class'
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# have it (which in turn is useful in conjunction with the SourceMixin
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# class).
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pass
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@property
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def closed(self):
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"""
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Returns ``True`` if the device is closed (see the :meth:`close`
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method). Once a device is closed you can no longer use any other
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methods or properties to control or query the device.
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"""
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raise NotImplementedError
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def _check_open(self):
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if self.closed:
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raise DeviceClosed(
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'%s is closed or uninitialized' % self.__class__.__name__)
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def __enter__(self):
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return self
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def __exit__(self, exc_type, exc_value, exc_tb):
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self.close()
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class Device(ValuesMixin, GPIOBase):
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"""
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Represents a single device of any type; GPIO-based, SPI-based, I2C-based,
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etc. This is the base class of the device hierarchy. It defines the basic
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services applicable to all devices (specifically the :attr:`is_active`
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property, the :attr:`value` property, and the :meth:`close` method).
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"""
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pin_factory = None # instance of a Factory sub-class
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def __init__(self, **kwargs):
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# Force pin_factory to be keyword-only, even in Python 2
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self.pin_factory = kwargs.pop('pin_factory', Device.pin_factory)
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if kwargs:
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raise TypeError("Device.__init__() got unexpected keyword "
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"argument '%s'" % kwargs.popitem()[0])
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super(Device, self).__init__()
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def __repr__(self):
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return "<gpiozero.%s object>" % (self.__class__.__name__)
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def _conflicts_with(self, other):
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"""
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Called by :meth:`Factory.reserve_pins` to test whether the *other*
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:class:`Device` using a common pin conflicts with this device's intent
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to use it. The default is ``True`` indicating that all devices conflict
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with common pins. Sub-classes may override this to permit more nuanced
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replies.
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"""
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return True
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@property
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def value(self):
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"""
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Returns a value representing the device's state. Frequently, this is a
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boolean value, or a number between 0 and 1 but some devices use larger
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ranges (e.g. -1 to +1) and composite devices usually use tuples to
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return the states of all their subordinate components.
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"""
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raise NotImplementedError
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@property
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def is_active(self):
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"""
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Returns ``True`` if the device is currently active and ``False``
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otherwise. This property is usually derived from :attr:`value`. Unlike
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:attr:`value`, this is *always* a boolean.
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"""
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return bool(self.value)
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class CompositeDevice(Device):
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"""
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Extends :class:`Device`. Represents a device composed of multiple devices
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like simple HATs, H-bridge motor controllers, robots composed of multiple
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motors, etc.
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The constructor accepts subordinate devices as positional or keyword
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arguments. Positional arguments form unnamed devices accessed via the
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:attr:`all` attribute, while keyword arguments are added to the device
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as named (read-only) attributes.
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:param list _order:
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If specified, this is the order of named items specified by keyword
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arguments (to ensure that the :attr:`value` tuple is constructed with a
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specific order). All keyword arguments *must* be included in the
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collection. If omitted, an alphabetically sorted order will be selected
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for keyword arguments.
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"""
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def __init__(self, *args, **kwargs):
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self._all = ()
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self._named = frozendict({})
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self._namedtuple = None
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self._order = kwargs.pop('_order', None)
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pin_factory = kwargs.pop('pin_factory', None)
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try:
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if self._order is None:
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self._order = sorted(kwargs.keys())
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else:
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for missing_name in set(kwargs.keys()) - set(self._order):
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raise CompositeDeviceBadOrder('%s missing from _order' % missing_name)
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self._order = tuple(self._order)
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for name in set(self._order) & set(dir(self)):
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raise CompositeDeviceBadName('%s is a reserved name' % name)
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for dev in chain(args, kwargs.values()):
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if not isinstance(dev, Device):
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raise CompositeDeviceBadDevice("%s doesn't inherit from Device" % dev)
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self._named = frozendict(kwargs)
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self._namedtuple = namedtuple('%sValue' % self.__class__.__name__, chain(
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('device_%d' % i for i in range(len(args))), self._order))
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except:
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for dev in chain(args, kwargs.values()):
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if isinstance(dev, Device):
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dev.close()
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raise
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self._all = args + tuple(kwargs[v] for v in self._order)
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kwargs = {'pin_factory': pin_factory} if pin_factory is not None else {}
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super(CompositeDevice, self).__init__(**kwargs)
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def __getattr__(self, name):
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# if _named doesn't exist yet, pretend it's an empty dict
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if name == '_named':
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return frozendict({})
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try:
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return self._named[name]
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except KeyError:
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raise AttributeError("no such attribute %s" % name)
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def __setattr__(self, name, value):
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# make named components read-only properties
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if name in self._named:
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raise AttributeError("can't set attribute %s" % name)
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return super(CompositeDevice, self).__setattr__(name, value)
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def __repr__(self):
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try:
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self._check_open()
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return "<gpiozero.%s object containing %d devices: %s and %d unnamed>" % (
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self.__class__.__name__,
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len(self), ','.join(self._order),
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len(self) - len(self._named)
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)
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except DeviceClosed:
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return "<gpiozero.%s object closed>" % (self.__class__.__name__)
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def __len__(self):
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return len(self._all)
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def __getitem__(self, index):
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return self._all[index]
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def __iter__(self):
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return iter(self._all)
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@property
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def all(self):
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# XXX Deprecate this in favour of using the instance as a container
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return self._all
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def close(self):
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if self._all:
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for device in self._all:
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device.close()
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self._all = ()
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@property
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def closed(self):
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return all(device.closed for device in self)
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@property
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def namedtuple(self):
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return self._namedtuple
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@property
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def value(self):
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return self.namedtuple(*(device.value for device in self))
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@property
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def is_active(self):
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return any(self.value)
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class GPIODevice(Device):
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"""
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Extends :class:`Device`. Represents a generic GPIO device and provides
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the services common to all single-pin GPIO devices (like ensuring two
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GPIO devices do no share a :attr:`pin`).
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:param int pin:
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The GPIO pin (in BCM numbering) that the device is connected to. If
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this is ``None``, :exc:`GPIOPinMissing` will be raised. If the pin is
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already in use by another device, :exc:`GPIOPinInUse` will be raised.
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"""
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def __init__(self, pin=None, **kwargs):
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super(GPIODevice, self).__init__(**kwargs)
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# self._pin must be set before any possible exceptions can be raised
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# because it's accessed in __del__. However, it mustn't be given the
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# value of pin until we've verified that it isn't already allocated
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self._pin = None
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if pin is None:
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raise GPIOPinMissing('No pin given')
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# Check you can reserve *before* constructing the pin
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self.pin_factory.reserve_pins(self, pin)
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pin = self.pin_factory.pin(pin)
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self._pin = pin
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self._active_state = True
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self._inactive_state = False
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def _state_to_value(self, state):
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return bool(state == self._active_state)
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def _read(self):
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try:
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return self._state_to_value(self.pin.state)
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except (AttributeError, TypeError):
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self._check_open()
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raise
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def close(self):
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super(GPIODevice, self).close()
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if self._pin is not None:
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self.pin_factory.release_pins(self, self._pin.number)
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self._pin.close()
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self._pin = None
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@property
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def closed(self):
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return self._pin is None
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def _check_open(self):
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try:
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super(GPIODevice, self)._check_open()
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except DeviceClosed as e:
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# For backwards compatibility; GPIODeviceClosed is deprecated
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raise GPIODeviceClosed(str(e))
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@property
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def pin(self):
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"""
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The :class:`Pin` that the device is connected to. This will be ``None``
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if the device has been closed (see the :meth:`close` method). When
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dealing with GPIO pins, query ``pin.number`` to discover the GPIO
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pin (in BCM numbering) that the device is connected to.
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"""
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return self._pin
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@property
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def value(self):
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return self._read()
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def __repr__(self):
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try:
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return "<gpiozero.%s object on pin %r, is_active=%s>" % (
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self.__class__.__name__, self.pin, self.is_active)
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except DeviceClosed:
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return "<gpiozero.%s object closed>" % self.__class__.__name__
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# Defined last to ensure Device is defined before attempting to load any pin
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# factory; pin factories want to load spi which in turn relies on devices (for
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# the soft-SPI implementation)
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def _default_pin_factory(name=os.getenv('GPIOZERO_PIN_FACTORY', None)):
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group = 'gpiozero_pin_factories'
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if name is None:
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# If no factory is explicitly specified, try various names in
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# "preferred" order. Note that in this case we only select from
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# gpiozero distribution so without explicitly specifying a name (via
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# the environment) it's impossible to auto-select a factory from
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# outside the base distribution
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#
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# We prefer RPi.GPIO here as it supports PWM, and all Pi revisions. If
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# no third-party libraries are available, however, we fall back to a
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# pure Python implementation which supports platforms like PyPy
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dist = pkg_resources.get_distribution('gpiozero')
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for name in ('rpigpio', 'rpio', 'pigpio', 'native'):
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try:
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return pkg_resources.load_entry_point(dist, group, name)()
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except Exception as e:
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warnings.warn(
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PinFactoryFallback(
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'Failed to load factory %s: %s' % (name, str(e))))
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raise BadPinFactory('Unable to load any default pin factory!')
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else:
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for factory in pkg_resources.iter_entry_points(group, name.lower()):
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return factory.load()()
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raise BadPinFactory('Unable to find pin factory "%s"' % name)
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def _devices_shutdown():
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if Device.pin_factory:
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with Device.pin_factory._res_lock:
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reserved_devices = {
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dev
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for ref_list in Device.pin_factory._reservations.values()
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for ref in ref_list
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for dev in (ref(),)
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if dev is not None
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}
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for dev in reserved_devices:
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dev.close()
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Device.pin_factory.close()
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Device.pin_factory = None
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def _shutdown():
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_threads_shutdown()
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_devices_shutdown()
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Device.pin_factory = _default_pin_factory()
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atexit.register(_shutdown)
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