How do I install the pythonstartup file so that it runs on command like python myfile.py?
I tried to install it into my /home/myuser<
On Windows you can put your startup script just about anywhere as long as you put its path into your PYTHONSTARTUP environment variable. On Windows the lettercase of environment variable names doesn't matter.
You can define the values of user and system environment variables as described in a somewhat related answer of mine here.