Create a Python script to read from /dev/ACMtty0

I have a Linux-based development board that runs Ubuntu. I need to interface it with a standard UART USB device that answers at /dev/ACMtty0. I need a Python script that will open serial communication, read the data until it hears the word "begin", then save that data to a file until it hears the word "end". Once the file is saved, it runs a piece of software with a console command. At all times, the script listens to the presence of serial comm. Once it's disconnected, the script halts. Upon reconnection, the script closes the previously opened piece of software, and starts everything over from the beginning (read data from "begin" to "end". P.S. Also, some post-processing of the saved file might be required. The data is streamed as a series of formatted strings (16 symbols), so some concatenation might be necessary. I have a simple ruby script that does that (attached), and I hope it could be implemented on Python as well.