Powershell script returns copyright information

I am executing a powershell script using python subprocess module.
subprocess.Popen((“powershell.exe”,”-ExecutionPolicy”,”bypass”,”-file”,{Powershell script}), stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()(0)
When I am executing, Powershell script returns copyright information instead of actual output. So I would like to know , why am getting the output and how to rectify that.
Thanks in Advance.