[PyQt] How to open a program with python without freezing

[LavaCreeperKing]

I am using PyQt. I have tried to use subprocess.run() and subprocess.call(). From what I understand is that it executes a command, but then waits for it to exit before I can continue and I don't want it to wait. I need it to run the program/file then allow me to also run other commands. A good way to describe what I want to do is basically create a program like the start menu in windows. Here is an example of some code that I tried where I create a new thread for launching programs.

class thread(QtCore.QThread):
    def __init__(self):
        super(thread, self).__init__()
        self.program = ''#path to program
        self.target = ''#path to file for program to open
    def run(self):
        while True:
            print('-')#prints when loop runs. Shows that loop stops after command executed until you close the created process
            if self.Program != '':
                call(r'%s' % self.program)#runs command
                self.program = ''#resets
            time.sleep(0.7)#Prevents CPU use by waiting a short time between runs

If I set the program to 'explorer' then the loop does not freeze, but I can't set a target file if I set the program to 'explorer' because I would have to set the target as the program I want to run so I won't be able to set a target file. Or I use explorer to open a file but It will only open with the default program set to open it.