TypeError: 'float' object has no attribute 'getitem'

First, as soon as the mouse is clicked, it saves itself in the bullets_array list the angle of the shot (which is the same angle as the player). Second, speed is given to the shot through the 'cos' and 'sin' and then its movement is limited to a maximum of 640px and 480px by the loop (thus, if overtaken the shot will be erased). Third, the shot is displayed on the screen at player's position (player_x, player_y)

The shot was supposed to start on player_x, player_y, walk straight through the cosine and sine and then "die" at the edge of the screen.

But the following sentence is shown:

  

line 53
  vel_x = math.cos (bullet [0]) * 10
  TypeError: 'float' object has no attribute 'getitem'

Here is the code:

#
# Title: Shoot The Zombies
# Author(s): John Redbeard, ("http://john-redbeard.tumblr.com/")
# 

import pygame
from pygame.locals import *
import math

    # Initiate Pygame
pygame.init()
width, height = 640, 480
screen=pygame.display.set_mode((width, height))
pygame.display.set_caption("Shoot the Zombies")
fps = 60
fpsclock = pygame.time.Clock()

    # Load images
player = pygame.image.load("images/player.png")
player_x = 100
player_y = 100
posplayer_x = 0
posplayer_y = 0

grass = pygame.image.load("images/grass.png")

bullet = pygame.image.load("images/bullet.png")
bullets_array = []

target = pygame.image.load("images/target.png")

    # Main Loop Game
while True:

    pygame.mouse.set_visible(False)

    screen.fill(False)

    # Load on screen the grass in isometric way
    for x in range(width/grass.get_width()+1):
        for y in range(height/grass.get_height()+1):
            screen.blit(grass,(x*100,y*100))

    # Load on screen the rotated-positioned-player
    mouse_position = pygame.mouse.get_pos()
    angle = math.atan2(mouse_position[0] - player_x, mouse_position[1] - player_y)
    player_rotate = pygame.transform.rotate(player, 360+angle*57.29)
    player_position = (player_x - player_rotate.get_rect().width/2, player_y - player_rotate.get_rect().height/2)
    screen.blit(player_rotate, player_position)

    # load on screen the rotated-posioted-bullets
    for bullet in bullets_array:
        vel_x = math.cos(bullet[0])*10
        vel_y = math.sin(bullet[1])*10
        bullet[0] += vel_x
        bullet[1] += vel_y
        if bullet[0] >640 or bullet[1] > 480:
            bullets_array.remove(bullet)
        bullet1 = pygame.transform.rotate(bullet, 360+angle*57.29)
        screen.blit(bullet1, (player_x, player_y))

    # Load on screen the target
    screen.blit(target, (mouse_position))

    # Display window
    pygame.display.flip()

    # Run events
    for event in pygame.event.get():
        if event.type==pygame.QUIT:
            pygame.quit() 
            exit(False)

    # Event: W/A/S/D (Keyboard) moving player
        elif event.type == KEYDOWN:
            if event.key == K_w:
                posplayer_y -= 3
            elif event.key == K_a:
                posplayer_x -= 3
            elif event.key == K_s:
                posplayer_y += 3
            elif event.key == K_d:
                posplayer_x += 3

        elif event.type == KEYUP:
            if event.key == K_w:
                posplayer_y = 0
            elif event.key == K_a:
                posplayer_x = 0
            elif event.key == K_s:
                posplayer_y= 0
            elif event.key == K_d:
                posplayer_x = 0

    # Event: Mouse click shoot the bullet
        elif event.type == MOUSEBUTTONDOWN:
            bullets_array.append(math.atan2(mouse_position[0] - player_x, mouse_position[1] - player_y))

    player_x += posplayer_x
    player_y +=posplayer_y

    fpsclock.tick(fps)