# 25. API - Exceptions

The following exceptions are defined by GPIO Zero. Please note that multiple inheritance is heavily used in the exception hierarchy to make testing for exceptions easier. For example, to capture any exception generated by GPIO Zero’s code:

    from gpiozero import *

    led = PWMLED(17)
    try:
        led.value = 2
    except GPIOZeroError:
        print('A GPIO Zero error occurred')

Since all GPIO Zero’s exceptions descend from `GPIOZeroError`, this will work. However, certain specific errors have multiple parents. For example, in the case that an out of range value is passed to `OutputDevice.value` you would expect a `ValueError` to be raised. In fact, a `OutputDeviceBadValue` error will be raised. However, note that this descends from both `GPIOZeroError` (indirectly) and from `ValueError` so you can still do the obvious:

    from gpiozero import *

    led = PWMLED(17)
    try:
        led.value = 2
    except ValueError:
        print('Bad value specified')

## 25.1. Errors

exception gpiozero.GPIOZeroError

  Bases: `Exception`

  Base class for all exceptions in GPIO Zero

exception gpiozero.DeviceClosed

  Bases: `GPIOZeroError`

  Error raised when an operation is attempted on a closed device

exception gpiozero.BadEventHandler

  Bases: `GPIOZeroError`, `ValueError`

  Error raised when an event handler with an incompatible prototype is specified

exception gpiozero.BadWaitTime

  Bases: `GPIOZeroError`, `ValueError`

  Error raised when an invalid wait time is specified

exception gpiozero.BadQueueLen

  Bases: `GPIOZeroError`, `ValueError`

  Error raised when non-positive queue length is specified

exception gpiozero.BadPinFactory

  Bases: `GPIOZeroError`, `ImportError`

  Error raised when an unknown pin factory name is specified

exception gpiozero.ZombieThread

  Bases: `GPIOZeroError`, `RuntimeError`

  Error raised when a thread fails to die within a given timeout

exception gpiozero.CompositeDeviceError

  Bases: `GPIOZeroError`

  Base class for errors specific to the CompositeDevice hierarchy

exception gpiozero.CompositeDeviceBadName

  Bases: `CompositeDeviceError`, `ValueError`

  Error raised when a composite device is constructed with a reserved name

exception gpiozero.CompositeDeviceBadOrder

  Bases: `CompositeDeviceError`, `ValueError`

  Error raised when a composite device is constructed with an incomplete order

exception gpiozero.CompositeDeviceBadDevice

  Bases: `CompositeDeviceError`, `ValueError`

  Error raised when a composite device is constructed with an object that doesn’t inherit from `Device`

exception gpiozero.EnergenieSocketMissing

  Bases: `CompositeDeviceError`, `ValueError`

  Error raised when socket number is not specified

exception gpiozero.EnergenieBadSocket

  Bases: `CompositeDeviceError`, `ValueError`

  Error raised when an invalid socket number is passed to `Energenie`

exception gpiozero.SPIError

  Bases: `GPIOZeroError`

  Base class for errors related to the SPI implementation

exception gpiozero.SPIBadArgs

  Bases: `SPIError`, `ValueError`

  Error raised when invalid arguments are given while constructing `SPIDevice`

exception gpiozero.SPIBadChannel

  Bases: `SPIError`, `ValueError`

  Error raised when an invalid channel is given to an `AnalogInputDevice`

exception gpiozero.SPIFixedClockMode

  Bases: `SPIError`, `AttributeError`

  Error raised when the SPI clock mode cannot be changed

exception gpiozero.SPIInvalidClockMode

  Bases: `SPIError`, `ValueError`

  Error raised when an invalid clock mode is given to an SPI implementation

exception gpiozero.SPIFixedBitOrder

  Bases: `SPIError`, `AttributeError`

  Error raised when the SPI bit-endianness cannot be changed

exception gpiozero.SPIFixedSelect

  Bases: `SPIError`, `AttributeError`

  Error raised when the SPI select polarity cannot be changed

exception gpiozero.SPIFixedWordSize

  Bases: `SPIError`, `AttributeError`

  Error raised when the number of bits per word cannot be changed

exception gpiozero.SPIInvalidWordSize

  Bases: `SPIError`, `ValueError`

  Error raised when an invalid (out of range) number of bits per word is specified

exception gpiozero.GPIODeviceError

  Bases: `GPIOZeroError`

  Base class for errors specific to the GPIODevice hierarchy

exception gpiozero.GPIODeviceClosed

  Bases: `GPIODeviceError`, `DeviceClosed`

  Deprecated descendent of `DeviceClosed`

exception gpiozero.GPIOPinInUse

  Bases: `GPIODeviceError`

  Error raised when attempting to use a pin already in use by another device

exception gpiozero.GPIOPinMissing

  Bases: `GPIODeviceError`, `ValueError`

  Error raised when a pin specification is not given

exception gpiozero.InputDeviceError

  Bases: `GPIODeviceError`

  Base class for errors specific to the InputDevice hierarchy

exception gpiozero.OutputDeviceError

  Bases: `GPIODeviceError`

  Base class for errors specified to the OutputDevice hierarchy

exception gpiozero.OutputDeviceBadValue

  Bases: `OutputDeviceError`, `ValueError`

  Error raised when `value` is set to an invalid value

exception gpiozero.PinError

  Bases: `GPIOZeroError`

  Base class for errors related to pin implementations

exception gpiozero.PinInvalidFunction

  Bases: `PinError`, `ValueError`

  Error raised when attempting to change the function of a pin to an invalid value

exception gpiozero.PinInvalidState

  Bases: `PinError`, `ValueError`

  Error raised when attempting to assign an invalid state to a pin

exception gpiozero.PinInvalidPull

  Bases: `PinError`, `ValueError`

  Error raised when attempting to assign an invalid pull-up to a pin

exception gpiozero.PinInvalidEdges

  Bases: `PinError`, `ValueError`

  Error raised when attempting to assign an invalid edge detection to a pin

exception gpiozero.PinInvalidBounce

  Bases: `PinError`, `ValueError`

  Error raised when attempting to assign an invalid bounce time to a pin

exception gpiozero.PinSetInput

  Bases: `PinError`, `AttributeError`

  Error raised when attempting to set a read-only pin

exception gpiozero.PinFixedPull

  Bases: `PinError`, `AttributeError`

  Error raised when attempting to set the pull of a pin with fixed pull-up

exception gpiozero.PinEdgeDetectUnsupported

  Bases: `PinError`, `AttributeError`

  Error raised when attempting to use edge detection on unsupported pins

exception gpiozero.PinUnsupported

  Bases: `PinError`, `NotImplementedError`

  Error raised when attempting to obtain a pin interface on unsupported pins

exception gpiozero.PinSPIUnsupported

  Bases: `PinError`, `NotImplementedError`

  Error raised when attempting to obtain an SPI interface on unsupported pins

exception gpiozero.PinPWMError

  Bases: `PinError`

  Base class for errors related to PWM implementations

exception gpiozero.PinPWMUnsupported

  Bases: `PinPWMError`, `AttributeError`

  Error raised when attempting to activate PWM on unsupported pins

exception gpiozero.PinPWMFixedValue

  Bases: `PinPWMError`, `AttributeError`

  Error raised when attempting to initialize PWM on an input pin

exception gpiozero.PinUnknownPi

  Bases: `PinError`, `RuntimeError`

  Error raised when gpiozero doesn’t recognize a revision of the Pi

exception gpiozero.PinMultiplePins

  Bases: `PinError`, `RuntimeError`

  Error raised when multiple pins support the requested function

exception gpiozero.PinNoPins

  Bases: `PinError`, `RuntimeError`

  Error raised when no pins support the requested function

exception gpiozero.PinInvalidPin

  Bases: `PinError`, `ValueError`

  Error raised when an invalid pin specification is provided

## 25.2. Warnings

exception gpiozero.GPIOZeroWarning

  Bases: `Warning`

  Base class for all warnings in GPIO Zero

exception gpiozero.DistanceSensorNoEcho

  Bases: `GPIOZeroWarning`

  Warning raised when the distance sensor sees no echo at all

exception gpiozero.SPIWarning

  Bases: `GPIOZeroWarning`

  Base class for warnings related to the SPI implementation

exception gpiozero.SPISoftwareFallback

  Bases: `SPIWarning`

  Warning raised when falling back to the SPI software implementation

exception gpiozero.PinWarning

  Bases: `GPIOZeroWarning`

  Base class for warnings related to pin implementations

exception gpiozero.PinFactoryFallback

  Bases: `PinWarning`

  Warning raised when a default pin factory fails to load and a fallback is tried

exception gpiozero.PinNonPhysical

  Bases: `PinWarning`

  Warning raised when a non-physical pin is specified in a constructor

exception gpiozero.ThresholdOutOfRange

  Bases: `GPIOZeroWarning`

  Warning raised when a threshold is out of range specified by min and max values

exception gpiozero.CallbackSetToNone

  Bases: `GPIOZeroWarning`

  Warning raised when a callback is set to None when its previous value was None