Week 3 - Section 2 - Graphics

5.4 - Move on

This screen that we have created is updated 60 times per second with the command clock.tick(60) but because we don't change anything it is the same picture 60 times a second.

Now we are going to move the rectangle. How can we do this? Which of the for numbers [50, 50, 50, 50] is the position of the rectangle? If you don't remember go to the previous page and look at the picture. 

We are going to replace the numbers with variables. Replace the draw command with these eight lines.

rect_x = 50    # X starting position of rectangle
rect_y = 50    # Y starting position of rectangle
speed_x = 5   # X speed of rectangle
speed_y = 5   # Y speed of rectangle
pygame.draw.rect(screen, WHITE, [rect_x, rect_y, 50,50])
rect_x += speed_x
rect_y += speed_y
print ("rect_x =", rect_x, "rect_y =", rect_y)

Nothing is happening. Why? Because 60 times per second rect_x and rect_y become 50 and then 55.

What should we do? Put the first four lines outside the loop. Cut and paste them before line 28 (#Main program loop) and don't forget the indentation.

Wow!! A moving rectangle!!