how can I rotate my image in pygame?

Question

I am making a simple space game and want my ship (xwingImg) to move freely. I need the ship to rotate when the a,d, and s keys are pressed. I thought that this would work: pg.transform.rotate(xwingImg, 90), but nothing seems to change.

import sys
import random
import pygame as pg


pg.init()
screen = pg.display.set_mode((1280, 800))
display_width = 1280
display_height= 800

black= (0,0,0)
white= (255,255,255)
red = (255,0,0)
blue_violet = (138,43,226)

xwingImg = pg.image.load('X-Wing.bmp').convert()
tieImg= pg.image.load('tiefighter.png').convert()
space=pg.image.load('space.jpg').convert()

BG_image = pg.image.load('space.jpg').convert()


def main():
    clock = pg.time.Clock()
    # Surfaces/images have a `get_rect` method which 
    # returns a rect with the dimensions of the image.
    player_rect = xwingImg.get_rect()
    player_rect.center = ( 640,400 )
    change_x = 0
    change_y = 0
    enemies = []
    spawn_counter = 30


    done = False

    while not done:
        for event in pg.event.get():
            if event.type == pg.QUIT:
                done = True
            if event.type == pg.KEYDOWN:
                if event.key == pg.K_d:
                    pg.transform.rotate(xwingImg, 90)
                    change_x = 5
                if event.key == pg.K_w:
                    change_y = -5
                if event.key == pg.K_s:
                    change_y= 5
                if event.key == pg.K_a:
                    change_x = -5
            if event.type == pg.KEYUP:
                if event.key == pg.K_d and change_x > 0:
                    change_x = 0
                if event.key == pg.K_a and change_x < 0:
                    change_x = 0
                if event.key == pg.K_w and change_y<0:
                    change_y=0
                if event.key == pg.K_s and change_y>0:
                    change_y=0



        # Spawn enemies if counter <= 0 then reset it.
        spawn_counter -= 1
        if spawn_counter <= 0:
            # Append an enemy rect. You can pass the position directly as an argument.
            enemies.append(tieImg.get_rect(topleft=(random.randrange(1280), -800 )))
            spawn_counter =  30


        # Update player_rect and enemies.
        player_rect.x += change_x
        player_rect.y += change_y
        for enemy_rect in enemies:
            enemy_rect.y += 5
            # Collision detection with pygame.Rect.colliderect.
            if player_rect.colliderect(enemy_rect):
                print('Collision!')

        # Draw everything.
        screen.blit(BG_image, (0,0))
        for enemy_rect in enemies:
            screen.blit(tieImg, enemy_rect)
        screen.blit(xwingImg, player_rect)

        if player_rect.x >display_width:
            player_rect.x = 0
        if player_rect.x < 0:
            player_rect.x= 1280
        if player_rect.y>display_height:
            player_rect.y = 0
        if player_rect.y < 0:
            player_rect.y= 800


        pg.display.flip()
        clock.tick(40)


if __name__ == '__main__':
    main()
    pg.quit()
    sys.exit()

Answer 1

pygame.transform.rotate() returns a new Surface with the rotated object on it. You are not using the returned Surface. You dont want to keep rotating an image repeatedly as rotate needs to pad the returned Surface to make it fit in a rect.

rotate(Surface, angle) -> Surface

Unfiltered counterclockwise rotation. The angle argument represents degrees and can be any floating point value. Negative angle amounts will rotate clockwise.

Unless rotating by 90 degree increments, the image will be padded larger to hold the new size. If the image has pixel alphas, the padded area will be transparent. Otherwise pygame will pick a color that matches the Surface colorkey or the topleft pixel value.

I would just keep track of the angle your image should be rotated then when a rotate event is detected change that angle. Then in your draw step blit the rotate image by that angle.

player_image = pg.transform.rotate(xwingImg, angle)
player_rect = player_image.get_rect()
player_rect.center = player_pos
screen.blit(player_image, player_rect)