import RPi.GPIO as gpio
import time

def init():
    gpio.setmode(gpio.BOARD)
    gpio.setup(7, gpio.OUT)
    gpio.setup(11, gpio.OUT)
    gpio.setup(13, gpio.OUT)
    gpio.setup(15, gpio.OUT)

def forward(tf):
    init()
    gpio.output(13, True)
    gpio.output(15, False)
    gpio.output(7, False)
    gpio.output(11, True)
    time.sleep(tf)
    gpio.cleanup()
    
def reverse(tf):
    init()
    gpio.output(13, False)
    gpio.output(15, True)
    gpio.output(7, True)
    gpio.output(11, False)
    time.sleep(tf)
    gpio.cleanup()

def turn_left(tf):
    init()
    gpio.output(7, True)
    gpio.output(11, True)
    gpio.output(13, True)
    gpio.output(15, False)
    time.sleep(tf)
    gpio.cleanup()

def turn_right(tf):
    init()
    gpio.output(7, False)
    gpio.output(13, False)
    gpio.output(15, False)
    gpio.output(11, True)
    time.sleep(tf)
    gpio.cleanup()
	
	
forward(1)
reverse(1)	
turn_left(1)
turn_right(1)
	
		

Now it is time to talk about turning the car, and one more concept. Each time you modify the pins, you need to reset them, or they will retain their last position plus any new changes. For this reason, it's best we instead run the init() function in every function. We're also going to now add turning left and right.