Print PDF to default printer after setting default printer in Python

Question

When I change default printer and then use;
win32api.shellexecute(0,'print',filename,None,'.',0)
all print jobs are still being sent to the first default printer set first in python

def printfile(filename):
    while True:
        printername=input("printername:")
        import win32print,time,win32api
        try:

            global defaultPrinter
            defaultPrinter=None
            defaultPrinter = win32print.GetDefaultPrinter()
            if defaultPrinter != printername:
                time.sleep(0.5)
                win32print.SetDefaultPrinter(printername)
            time.sleep(0.5)
                
            win32api.ShellExecute (
            0,
            "print",
            filename,
            None, ".", 0)       
            
            time.sleep(3)
            
            win32print.SetDefaultPrinter(defaultPrinter)
        except Exception as err:
            print(err)
        
printfile('Black.pdf')

I tried to change the default printer through my program but all print jobs will send to the first default printer set at the beginning of my program running.