Player not moving smoothly in pygame

Question

So I made this game in pygame and I want the player to move and it moves but not in the way I want it.It kinda teleports and then goes back to walking normally and then it teleports again and so on.

This is the code by now:

import pygame

pygame.init()

screen = pygame.display.set_mode((1000,1000))
clock = pygame.time.Clock()


playerX = 100
playerY = 100

def ecranAlb():
    WHITE = [255,255,255]
    screen.fill(WHITE)
    
def player():
    global playerX, playerY
    playerImg = pygame.image.load('knight.png')
    playerImg = pygame.transform.scale(playerImg,(250,150))
    screen.blit(playerImg,(playerX,playerY))
    
    vel = 10

    keys = pygame.key.get_pressed()

    if keys[pygame.K_LEFT]:
        playerX -= vel
    if keys[pygame.K_RIGHT]:
        playerX += vel
    if keys[pygame.K_UP]:
        playerY -= vel
    if keys[pygame.K_DOWN]:
        playerY += vel





running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
    ecranAlb()
    player()
    clock.tick(200)
    pygame.display.flip()

Answer 1

Do not load the image in the player function. pygame.image.load causes the lag, as it is very time consuming. Load the image once during initialization and us the loaded image inside the function.

Ensure that the image Surface has the same format as the display Surface. Use convert() (or convert_alpha()) to create a Surface that has the same pixel format. This improves performance when the image is blit on the display, because the formats are compatible and blit does not need to perform an implicit transformation.

playerImg = pygame.image.load('knight.png').convert_alpha()
playerImg = pygame.transform.scale(playerImg,(250,150))
vel = 10

def player():
    global playerX, playerY
    
    keys = pygame.key.get_pressed()
    if keys[pygame.K_LEFT]:
        playerX -= vel
    if keys[pygame.K_RIGHT]:
        playerX += vel
    if keys[pygame.K_UP]:
        playerY -= vel
    if keys[pygame.K_DOWN]:
        playerY += vel

    screen.blit(playerImg,(playerX,playerY))