The fastest and easiest way to run all Python files in a directory is to use loops. You can use bash to do this for you.
For example, create a new file called run_all_py.sh and write the following in it:
for f in *.py; do python"$f"; done
Now run the file using
$ bash run_all_py.sh
You could also use xargs to parallely execute these files(Only available on UNIX).
$ ls *.py|xargs -n 1 -P 4 python