When I do rosrun mypython.py, I have error :
/usr/bin/env: ‘python\r’ : No such file or directory
However python mypython.py work fine,
use of rosrun requires a ROS package name that the python script was developed under.
So lets say you made a catkin_ws workspace for python tool and it was located in ~/catkin_ws/mypythonproject There are rules for how this is done that is beyond this explaination so I suggest you look here as a starting point: rospy_tutorials/Tutorials/Makefile - ROS Wiki
Only after you have a ROS package for your python tool can you use rosrun and you would then use:
rosrun mypythonproject mypython.py
You cannot just use rosrun without a ROS project. This is a bit of overhead but if you are going to run this script from a ROS launch file for example, you really should form a ros package.
Hope this helps.