Use Python to split a string and output each token into seperate lines?

$ echo '"a1","a2","a3"'|python3 -c "import sys; print('\n'.join(sys.stdin.read().splitlines()), sep='\n');"
"a1","a2","a3"

$ echo '"a1","a2","a3"'|python3 -c "import sys; [print(a, sep='\n') for a in sys.stdin.read().splitlines()];"
"a1","a2","a3"

$ echo '"a1","a2","a3"'|python3 -c "import sys,pprint; pprint.pprint('\n'.join(sys.stdin.read().splitlines()));"
'"a1","a2","a3"'

I have tried many different methods but none of them work for me.
I would like to print each token into a seperate line.

Question> How can I get the following results?

"a1"
"a2"
"a3"

Thank you

>Solution :

Split on comma instead.

print('\n'.join(sys.stdin.read().split(',')))