Removed redundant weakref references

Also tweaked a couple of minor bits (SPI bus init mask) and unused
_get_address override

gpiozero/pins/local.py

@@ -7,7 +7,6 @@ from __future__ import (
 str = type('')
 
 import io
-import weakref
 import warnings
 
 try:

gpiozero/pins/native.py

@@ -13,7 +13,6 @@ import mmap
 import errno
 import struct
 import warnings
-import weakref
 from time import sleep
 from threading import Thread, Event, Lock
 from collections import Counter

gpiozero/pins/pigpiod.py

@@ -179,9 +179,6 @@ class PiGPIOPin(PiPin):
             self.function = 'input'
             self.pull = 'up' if self.factory.pi_info.pulled_up('GPIO%d' % self.number) else 'floating'
 
-    def _get_address(self):
-        return self.factory.address + ('GPIO%d' % self.number,)
-
     def _get_function(self):
         return self.GPIO_FUNCTION_NAMES[self.factory.connection.get_mode(self.number)]
 

gpiozero/pins/rpigpio.py

@@ -7,7 +7,6 @@ from __future__ import (
 str = type('')
 
 import warnings
-import weakref
 from RPi import GPIO
 
 from .local import LocalPiFactory, LocalPiPin

gpiozero/pins/rpio.py

@@ -8,7 +8,6 @@ str = type('')
 
 
 import warnings
-import weakref
 import RPIO
 import RPIO.PWM
 from RPIO.Exceptions import InvalidChannelException

gpiozero/pins/spi.py

@@ -64,9 +64,14 @@ class SPISoftwareBus(SharedMixin, Device):
         """
         result = []
         with self.lock:
-            shift = operator.lshift if lsb_first else operator.rshift
+            if lsb_first:
+                shift = operator.lshift
+                init_mask = 1
+            else:
+                shift = operator.rshift
+                init_mask = 1 << (bits_per_word - 1)
             for write_word in data:
-                mask = 1 if lsb_first else 1 << (bits_per_word - 1)
+                mask = init_mask
                 read_word = 0
                 for _ in range(bits_per_word):
                     if self.mosi is not None: