How do I run a python pgm from command line

python3 filename

Replace filename with the filename of the program. If you have not navigated (with the cd command) to the directory in which the program resides, then you'll have to either do that, or specify its absolute path (or its path relative to the current directory). For example, I might use:

cd /home/ek/source
python3 hello.py

Or I might instead use:

python3 /home/ek/source/hello.py

If your program begins with a "shebang" line, like

#!/usr/bin/env python3

and it is marked executable, then you can run it like:

./filename

For example:

cd /home/ek/source
chmod +x hello.py
./hello.py