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https://github.com/KevinMidboe/python-gpiozero.git
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The source/values toolkit
Me and my big mouth. No sooner do I declare the base classes "relatively stable" than I go and mess around with it all again. Anyway, this is the long promised set of utilities to make source/values more interesting. It includes a few interesting little utility functions, a whole bunch of examples and introduces the notion of "pseudo" devices with no (obvious) hardware representation like a time-of-day device. This necessitated making the event system a little more generic (it's not exclusive the GPIO devices after all; no reason we can't use it on composite devices in future) and by this point the mixins have gotten large enough to justify their own module. The pseudo-devices are a bit spartan and basic at the moment but I'm sure there'll be plenty of future ideas...
This commit is contained in:
Dave Jones
@@ -15,6 +15,10 @@ from types import FunctionType
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from threading import RLock
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from .threads import GPIOThread, _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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DeviceClosed,
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GPIOPinMissing,
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@@ -201,127 +205,35 @@ class GPIOBase(GPIOMeta(nstr('GPIOBase'), (), {})):
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self.close()
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class ValuesMixin(object):
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"""
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Adds a :attr:`values` property to the class which returns an infinite
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generator of readings from the :attr:`value` property.
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.. note::
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Use this mixin *first* in the parent class list.
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"""
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@property
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def values(self):
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"""
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An infinite iterator of values read from `value`.
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"""
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while True:
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try:
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yield self.value
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except GPIODeviceClosed:
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break
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class SourceMixin(object):
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"""
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Adds a :attr:`source` property to the class which, given an iterable,
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sets :attr:`value` to each member of that iterable until it is exhausted.
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.. note::
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Use this mixin *first* in the parent class list.
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"""
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def __init__(self, *args, **kwargs):
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self._source = None
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self._source_thread = None
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self._source_delay = 0.01
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super(SourceMixin, self).__init__(*args, **kwargs)
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def close(self):
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try:
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super(SourceMixin, self).close()
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except AttributeError:
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pass
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self.source = None
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def _copy_values(self, source):
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for v in source:
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self.value = v
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if self._source_thread.stopping.wait(self._source_delay):
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break
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@property
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def source_delay(self):
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"""
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The delay (measured in seconds) in the loop used to read values from
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:attr:`source`. Defaults to 0.01 seconds which is generally sufficient
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to keep CPU usage to a minimum while providing adequate responsiveness.
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"""
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return self._source_delay
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@source_delay.setter
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def source_delay(self, value):
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if value < 0:
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raise GPIOBadSourceDelay('source_delay must be 0 or greater')
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self._source_delay = float(value)
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@property
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def source(self):
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"""
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The iterable to use as a source of values for :attr:`value`.
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"""
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return self._source
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@source.setter
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def source(self, value):
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if self._source_thread is not None:
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self._source_thread.stop()
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self._source_thread = None
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self._source = value
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if value is not None:
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self._source_thread = GPIOThread(target=self._copy_values, args=(value,))
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self._source_thread.start()
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class SharedMixin(object):
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"""
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This mixin marks a class as "shared". In this case, the meta-class
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(GPIOMeta) will use :meth:`_shared_key` to convert the constructor
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arguments to an immutable key, and will check whether any existing
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instances match that key. If they do, they will be returned by the
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constructor instead of a new instance. An internal reference counter is
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used to determine how many times an instance has been "constructed" in this
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way.
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When :meth:`close` is called, an internal reference counter will be
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decremented and the instance will only close when it reaches zero.
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"""
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_INSTANCES = {}
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def __del__(self):
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self._refs = 0
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super(SharedMixin, self).__del__()
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@classmethod
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def _shared_key(cls, *args, **kwargs):
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"""
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Given the constructor arguments, returns an immutable key representing
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the instance. The default simply assumes all positional arguments are
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immutable.
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"""
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return args
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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.
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etc. This is the base class of the device hierarchy. It defines the
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basic services applicable to all devices (specifically thhe :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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def __repr__(self):
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return "<gpiozero.%s object>" % (self.__class__.__name__)
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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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return 0
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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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@@ -417,15 +329,16 @@ class CompositeDevice(Device):
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def value(self):
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return self.tuple(*(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.
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This is the class at the root of the gpiozero class hierarchy. It handles
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ensuring that two GPIO devices do not share the same pin, and provides
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basic services applicable to all devices (specifically the :attr:`pin`
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property, :attr:`is_active` property, and the :attr:`close` method).
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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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@@ -494,14 +407,8 @@ class GPIODevice(Device):
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@property
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def value(self):
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"""
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Returns ``True`` if the device is currently active and ``False``
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otherwise.
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"""
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return self._read()
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is_active = value
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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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