how to run new python shell using python shell itself

Question

is there any way i can run another python program in a new shell/window using another currently active python program for example

#file1.py is executing a loop>>>
for I in range (0,9):
    #the thing here I wish to do is 
    while I==5:
    #open file2.py in new python shell in a new window and the for loop moves on 

Note >>>I do not want the loop to wait for file2.py to do its work i wish to run both file2.py and file1.py executing at the same time
i tried using "subprocess" and it made file2.py run in same window(shell) which in turn caused file1.py to wait until file2.py did its job