A Python library for controlling the Raspberry Pi's GPIO pins without running as root.

The library depends on:

• Python 3.1
• Quick2Wire GPIO Admin

To install Python 3.1 run the command:

sudo apt-get install python3

To install Quick2Wire GPIO Admin, follow the instructions at http://github.com/quick2wire/quick2wire-gpio-admin

The library is currently under active development, so we do not recommend installing it into the system-wide Python libraries. Instead, you can either use it with no installation or use virtualenv, to do all your development within an isolated Python environment, and install into that.

To use the library without any installation, add the full path of the src subdirectory of the source tree to the PYTHONPATH environment variable. For example:

export QUICK2WIRE_API_HOME=[the directory cloned from Git or unpacked from the source archive]
export PYTHONPATH=$PYTHONPATH:$QUICK2WIRE_API_HOME/src

To install into a virtualenv, make the virtualenv active and run:

python setup.py install

The GPIO pins are controlled by Pin objects. Python program must import the Pin class from the quick2wire.gpio module:

from quick2wire.gpio import Pin

Then you can create a Pin. The Pin's constructor takes two arguments: the header pin number and whether the pin is to be used for input or output.

out_pin = Pin(12, Pin.Out)
in_pin = Pin(16, Pin.In)

When you have a Pin instance you can read or write its value. A value of 1 is high, a value of 0 is low.

out_pin.value = 1
print(in_pin.value)

When you have finished using the pin, you must unexport it:

out_pin.unexport()
in_pin.unexport()

Putting it all together into a single program:

from quick2wire.gpio import Pin

out_pin = Pin(12, Pin.Out)
in_pin = Pin(16, Pin.In)

out_pin.value = 1
print(in_pin.value)

out_pin.unexport()
in_pin.unexport()

Another example, blinking an LED attached to header pin 12 and unexporting the pin when the user quits the program with Control-C.

from time import sleep
from quick2wire.gpio import Pin

pin = Pin(12, Pin.Out)

try:
    while True:
        pin.value = 1 - pin.value
        sleep(1)
except KeyboardInterrupt:
    pin.unexport()