Why the error

import pygame
pygame.init()

scrWidth = 640
scrHeight = 480
left = False
right = False
walkCount = 0
x = 1
y = 400
width = 75
height = 80
vel = 5
isJump = False
jumpCount = 10
clock = pygame.time.Clock()

window = pygame.display.set_mode((scrWidth,scrHeight))
pygame.display.set_caption("Game")
walkRight = [pygame.image.load('DefaultWalk1.png'),pygame.image.load('DefaultWalk2.png')]
walkLeft = [pygame.image.load('Default2Walk1.png'),pygame.image.load('Default2Walk2.png')]
bg = pygame.image.load("background.png")
char = pygame.image.load ("Default.png")



def Draw():
    global walkCount
    window.blit(bg,(0,0))
    if walkCount +1 > 20:
       walkCount = 0
    if left:
        walkCount += 1
        window.blit[walkLeft(x,y)]
    elif right:
        walkCount += 1
        window.blit[walkRight(x,y)]
    else:
        window.blit(char,(x,y))
    pygame.display.update()


run = True
while run:
    clock.tick(20)

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            run = False
    keys = pygame.key.get_pressed()
    if keys [pygame.K_a]and x > vel:
        x -= vel
        left = True
        right = False

    elif keys [pygame.K_d]and x < 600:
        x+= vel
        right = True
        left = False
    else:
        right = False
        left = False
        walkCount = 0
    if not(isJump):
        if keys [pygame.K_SPACE]:
           isJump = True
           right = False
           left = False
           walkCount = 0
    else:
        if jumpCount >= -10:
            neg = 1
            if jumpCount < 0:
                neg = -1
            y -= (jumpCount ** 2)* 0.5 * neg
            jumpCount -= 1
        else:
            isJump = False
            jumpCount = 10

    Draw()
pygame.quit()