This item will create a good bridge for your learning purpose. All the Raspberry pi pins are “redefined” into arduino style pins, so you can focus on python programming and higher level controlling by using RPI.
Fully compatible with Arduino, including Arduino shields
Plugs into Raspberry-Pi GPIO header
Voltage safe – Bidirectional translator automatically converts between 3.3V for Raspberry-Pi and 5V for Arduino
Most important pins includes UART, SPI, IIC, GPIOs are mapped onto the board, only pins A0-A3 is not in used.