Why i can't use cmd to open the psychopy builder?even if i add the env to windows

once i install the psychopy and then i uninstall it,like the question i say,can anyone help me?
Traceback (most recent call last):
** File “”, line 1, in **
NameError: name ‘psychopy’ is not defined

Not a big problem, but it bothers me a lot, thank you for your help