from __future__ import (

unicode_literals,

print_function,

absolute_import,

division,

)

nstr = str

str = type('')

import os

import atexit

import weakref

from collections import namedtuple

from itertools import chain

from types import FunctionType

from threading import RLock

import pkg_resources

from .threads import _threads_shutdown

from .pins import _pins_shutdown

from .mixins import (

ValuesMixin,

SharedMixin,

)

from .exc import (

BadPinFactory,

DeviceClosed,

CompositeDeviceBadName,

CompositeDeviceBadOrder,

CompositeDeviceBadDevice,

GPIOPinMissing,

GPIOPinInUse,

GPIODeviceClosed,

)

from .compat import frozendict

def _default_pin_factory(name=os.getenv('GPIOZERO_PIN_FACTORY', None)):

group = 'gpiozero_pin_factories'

if name is None:

# If no factory is explicitly specified, try various names in

# "preferred" order. Note that in this case we only select from

# gpiozero distribution so without explicitly specifying a name (via

# the environment) it's impossible to auto-select a factory from

# outside the base distribution

#

# We prefer RPi.GPIO here as it supports PWM, and all Pi revisions. If

# no third-party libraries are available, however, we fall back to a

# pure Python implementation which supports platforms like PyPy

dist = pkg_resources.get_distribution('gpiozero')

for name in ('RPiGPIOPin', 'RPIOPin', 'PiGPIOPin', 'NativePin'):

try:

return pkg_resources.load_entry_point(dist, group, name)

except ImportError:

pass

raise BadPinFactory('Unable to locate any default pin factory!')

else:

for factory in pkg_resources.iter_entry_points(group, name):

return factory.load()

raise BadPinFactory('Unable to locate pin factory "%s"' % name)

pin_factory = _default_pin_factory()

_PINS = set()

_PINS_LOCK = RLock() # Yes, this needs to be re-entrant

def _shutdown():

_threads_shutdown()

with _PINS_LOCK:

while _PINS:

_PINS.pop().close()

# Any cleanup routines registered by pins libraries must be called *after*

# cleanup of pin objects used by devices

_pins_shutdown()

atexit.register(_shutdown)

class GPIOMeta(type):

# NOTE Yes, this is a metaclass. Don't be scared - it's a simple one.

def __new__(mcls, name, bases, cls_dict):

# Construct the class as normal

cls = super(GPIOMeta, mcls).__new__(mcls, name, bases, cls_dict)

# If there's a method in the class which has no docstring, search

# the base classes recursively for a docstring to copy

for attr_name, attr in cls_dict.items():

if isinstance(attr, FunctionType) and not attr.__doc__:

for base_cls in cls.__mro__:

if hasattr(base_cls, attr_name):

base_fn = getattr(base_cls, attr_name)

if base_fn.__doc__:

attr.__doc__ = base_fn.__doc__

break

return cls

def __call__(cls, *args, **kwargs):

# Make sure cls has GPIOBase somewhere in its ancestry (otherwise

# setting __attrs__ below will be rather pointless)

assert issubclass(cls, GPIOBase)

if issubclass(cls, SharedMixin):

# If SharedMixin appears in the class' ancestry, convert the

# constructor arguments to a key and check whether an instance

# already exists. Only construct the instance if the key's new.

key = cls._shared_key(*args, **kwargs)

try:

self = cls._INSTANCES[key]

self._refs += 1

except (KeyError, ReferenceError) as e:

self = super(GPIOMeta, cls).__call__(*args, **kwargs)

self._refs = 1

# Replace the close method with one that merely decrements

# the refs counter and calls the original close method when

# it reaches zero

old_close = self.close

def close():

self._refs = max(0, self._refs - 1)

if not self._refs:

try:

old_close()

finally:

try:

del cls._INSTANCES[key]

except KeyError:

# If the _refs go negative (too many closes)

# just ignore the resulting KeyError here -

# it's already gone

pass

self.close = close

cls._INSTANCES[key] = weakref.proxy(self)

else:

# Construct the instance as normal

self = super(GPIOMeta, cls).__call__(*args, **kwargs)

# At this point __new__ and __init__ have all been run. We now fix the

# set of attributes on the class by dir'ing the instance and creating a

# frozenset of the result called __attrs__ (which is queried by

# GPIOBase.__setattr__). An exception is made for SharedMixin devices

# which can be constructed multiple times, returning the same instance

if not issubclass(cls, SharedMixin) or self._refs == 1:

self.__attrs__ = frozenset(dir(self))

return self

# Cross-version compatible method of using a metaclass

class GPIOBase(GPIOMeta(nstr('GPIOBase'), (), {})):

def __setattr__(self, name, value):

# This overridden __setattr__ simply ensures that additional attributes

# cannot be set on the class after construction (it manages this in

# conjunction with the meta-class above). Traditionally, this is

# managed with __slots__; however, this doesn't work with Python's

# multiple inheritance system which we need to use in order to avoid

# repeating the "source" and "values" property code in myriad places

if hasattr(self, '__attrs__') and name not in self.__attrs__:

raise AttributeError(

"'%s' object has no attribute '%s'" % (

self.__class__.__name__, name))

return super(GPIOBase, self).__setattr__(name, value)

def __del__(self):

self.close()

def close(self):

"""

Shut down the device and release all associated resources. This method

can be called on an already closed device without raising an exception.

This method is primarily intended for interactive use at the command

line. It disables the device and releases its pin(s) for use by another

device.

You can attempt to do this simply by deleting an object, but unless

you've cleaned up all references to the object this may not work (even

if you've cleaned up all references, there's still no guarantee the

garbage collector will actually delete the object at that point). By

contrast, the close method provides a means of ensuring that the object

is shut down.

For example, if you have a breadboard with a buzzer connected to pin

16, but then wish to attach an LED instead:

>>> from gpiozero import *

>>> bz = Buzzer(16)

>>> bz.on()

>>> bz.off()

>>> bz.close()

>>> led = LED(16)

>>> led.blink()

:class:`Device` descendents can also be used as context managers using

the :keyword:`with` statement. For example:

>>> from gpiozero import *

>>> with Buzzer(16) as bz:

... bz.on()

...

>>> with LED(16) as led:

... led.on()

...

"""

# This is a placeholder which is simply here to ensure close() can be

# safely called from subclasses without worrying whether super-class'

# have it (which in turn is useful in conjunction with the SourceMixin

# class).

pass

@property

def closed(self):

"""

Returns ``True`` if the device is closed (see the :meth:`close`

method). Once a device is closed you can no longer use any other

methods or properties to control or query the device.

"""

raise NotImplementedError

def _check_open(self):

if self.closed:

raise DeviceClosed(

'%s is closed or uninitialized' % self.__class__.__name__)

def __enter__(self):

return self

def __exit__(self, exc_type, exc_value, exc_tb):

self.close()

class Device(ValuesMixin, GPIOBase):

"""

Represents a single device of any type; GPIO-based, SPI-based, I2C-based,

etc. This is the base class of the device hierarchy. It defines the

basic services applicable to all devices (specifically the :attr:`is_active`

property, the :attr:`value` property, and the :meth:`close` method).

"""

def __repr__(self):

return "<gpiozero.%s object>" % (self.__class__.__name__)

@property

def value(self):

"""

Returns a value representing the device's state. Frequently, this is a

boolean value, or a number between 0 and 1 but some devices use larger

ranges (e.g. -1 to +1) and composite devices usually use tuples to

return the states of all their subordinate components.

"""

raise NotImplementedError

@property

def is_active(self):

"""

Returns ``True`` if the device is currently active and ``False``

otherwise. This property is usually derived from :attr:`value`. Unlike

:attr:`value`, this is *always* a boolean.

"""

return bool(self.value)

class CompositeDevice(Device):

"""

Extends :class:`Device`. Represents a device composed of multiple devices

like simple HATs, H-bridge motor controllers, robots composed of multiple

motors, etc.

The constructor accepts subordinate devices as positional or keyword

arguments. Positional arguments form unnamed devices accessed via the

:attr:`all` attribute, while keyword arguments are added to the device

as named (read-only) attributes.

:param list _order:

If specified, this is the order of named items specified by keyword

arguments (to ensure that the :attr:`value` tuple is constructed with a

specific order). All keyword arguments *must* be included in the

collection. If omitted, an alphabetically sorted order will be selected

for keyword arguments.

"""

def __init__(self, *args, **kwargs):

self._all = ()

self._named = frozendict({})

self._namedtuple = None

self._order = kwargs.pop('_order', None)

if self._order is None:

self._order = sorted(kwargs.keys())

else:

for missing_name in set(kwargs.keys()) - set(self._order):

raise CompositeDeviceBadOrder('%s missing from _order' % missing_name)

self._order = tuple(self._order)

super(CompositeDevice, self).__init__()

for name in set(self._order) & set(dir(self)):

raise CompositeDeviceBadName('%s is a reserved name' % name)

self._all = args + tuple(kwargs[v] for v in self._order)

for dev in self._all:

if not isinstance(dev, Device):

raise CompositeDeviceBadDevice("%s doesn't inherit from Device" % dev)

self._named = frozendict(kwargs)

self._namedtuple = namedtuple('%sValue' % self.__class__.__name__, chain(

(str(i) for i in range(len(args))), self._order),

rename=True)

def __getattr__(self, name):

# if _named doesn't exist yet, pretend it's an empty dict

if name == '_named':

return frozendict({})

try:

return self._named[name]

except KeyError:

raise AttributeError("no such attribute %s" % name)

def __setattr__(self, name, value):

# make named components read-only properties

if name in self._named:

raise AttributeError("can't set attribute %s" % name)

return super(CompositeDevice, self).__setattr__(name, value)

def __repr__(self):

try:

self._check_open()

return "<gpiozero.%s object containing %d devices: %s and %d unnamed>" % (

self.__class__.__name__,

len(self), ','.join(self._order),

len(self) - len(self._named)

)

except DeviceClosed:

return "<gpiozero.%s object closed>" % (self.__class__.__name__)

def __len__(self):

return len(self._all)

def __getitem__(self, index):

return self._all[index]

def __iter__(self):

return iter(self._all)

@property

def all(self):

# XXX Deprecate this in favour of using the instance as a container

return self._all

def close(self):

if self._all:

for device in self._all:

device.close()

@property

def closed(self):

return all(device.closed for device in self)

@property

def namedtuple(self):

return self._namedtuple

@property

def value(self):

return self.namedtuple(*(device.value for device in self))

@property

def is_active(self):

return any(self.value)

class GPIODevice(Device):

"""

Extends :class:`Device`. Represents a generic GPIO device and provides

the services common to all single-pin GPIO devices (like ensuring two

GPIO devices do no share a :attr:`pin`).

:param int pin:

The GPIO pin (in BCM numbering) that the device is connected to. If

this is ``None``, :exc:`GPIOPinMissing` will be raised. If the pin is

already in use by another device, :exc:`GPIOPinInUse` will be raised.

"""

def __init__(self, pin=None):

super(GPIODevice, self).__init__()

# self._pin must be set before any possible exceptions can be raised

# because it's accessed in __del__. However, it mustn't be given the

# value of pin until we've verified that it isn't already allocated

self._pin = None

if pin is None:

raise GPIOPinMissing('No pin given')

if isinstance(pin, int):

pin = pin_factory(pin)

with _PINS_LOCK:

if pin in _PINS:

raise GPIOPinInUse(

'pin %r is already in use by another gpiozero object' % pin

)

_PINS.add(pin)

self._pin = pin

self._active_state = True

self._inactive_state = False

def _state_to_value(self, state):

return bool(state == self._active_state)

def _read(self):

try:

return self._state_to_value(self.pin.state)

except (AttributeError, TypeError):

self._check_open()

raise

def close(self):

super(GPIODevice, self).close()

with _PINS_LOCK:

pin = self._pin

self._pin = None

if pin in _PINS:

_PINS.remove(pin)

pin.close()

@property

def closed(self):

return self._pin is None

def _check_open(self):

try:

super(GPIODevice, self)._check_open()

except DeviceClosed as e:

# For backwards compatibility; GPIODeviceClosed is deprecated

raise GPIODeviceClosed(str(e))

@property

def pin(self):

"""

The :class:`Pin` that the device is connected to. This will be ``None``

if the device has been closed (see the :meth:`close` method). When

dealing with GPIO pins, query ``pin.number`` to discover the GPIO

pin (in BCM numbering) that the device is connected to.

"""

return self._pin

@property

def value(self):

return self._read()

def __repr__(self):

try:

return "<gpiozero.%s object on pin %r, is_active=%s>" % (

self.__class__.__name__, self.pin, self.is_active)

except DeviceClosed:

return "<gpiozero.%s object closed>" % self.__class__.__name__