This is a Python library for use with the PCF8574 I2C IO expander chip. It abstracts the 8 bit IO port as a Python list, and allows the read/writing of individual pins or the whole port at once.
The library depends on the smbus-cffi package. You may need to apt-get install libffi-dev if you're on a debian based system. Otherwise, simply:
pip install pcf8574
In [1]: from pcf8574 import PCF8574
In [2]: i2c_port_num = 1
In [3]: pcf_address = 0x20
In [4]: pcf = PCF8574(i2c_port_num, pcf_address)
In [5]: pcf.port
Out[5]: [True, True, True, True, True, True, True, True]
In [6]: pcf.port[0] = False
In [7]: pcf.port
Out[7]: [False, True, True, True, True, True, True, True]
In [8]: pcf.port = [True, False, True, False, True, False, True, False]
In [9]: pcf.port
Out[9]: [True, False, True, False, True, False, True, False]
In [10]: pcf.port[7]
Out[10]: False
In [11]: pcf.port[6]
Out[11]: True