do you mean you want to program a Raspberry Pi to talk to a PSOC5?
The Rpi side is the same as connecting any other peripheral you can refer to http://elinux.org/RPi_Serial_Connection.
On the PSOC side you will want to use the UART component and route the output to iopins. if you are using a CY8CKIT-050 or building your own PSOC board you can select 3.3v for VDDIO so you won't need any level converter. The PSOC sidehas to be done using PSOC Creator so it's done in C not in phyton.