flip vs update for pygame display?

flip swaps entire back buffer; equivalent to update() with no args. update(rectangles) updates only specified regions. For full-screen redraw, flip is fine; for partial-screen UI, update with dirty rects is faster.

vsync flag on set_mode applies to flip. update doesn't always honor vsync — can produce tearing if not paired with manual frame pacing.

Dirty rect technique?

Track per-frame changed rectangles. Pass list to update. Skips redrawing static regions; massive speedup for UI-heavy scenes.

Fix: Pygame display.flip vs display.update Stutter

Quick answer: flip() for full-screen + vsync. update(dirty_rects) for partial-screen UI. Don’t mix.

UI game stutters at 60fps. Each frame redraws everything via flip when only inventory changed. update with dirty rects is the fix.

The Fix

# Full screen redraw
screen.fill((0,0,0))
draw_world()
pygame.display.flip()

# Partial: dirty rect optimization
dirty = []
for sprite in changed_sprites:
    rect = sprite.draw(screen)
    dirty.append(rect)
pygame.display.update(dirty)

Track which rectangles changed; update only those. Static background untouched.

Verifying

UI scene goes from 30fps to 60fps with dirty rect approach. Profile per-frame draw time.

“flip for whole. update for parts.”

Related Issues

For Clock.tick busy_loop, see tick busy. For HiDPI text, see HiDPI.

Dirty rects. Update only changed.