I am trying to make bullets bounce of walls, but I can't figure out how to correctly do the collision detection. What I am currently doing is iterating through all the solid blocks and if the bullet hits the bottom, top or sides, its vector is adjusted accordingly. However, sometimes when I shoot, the bullet doesn't bounce, I think it's when I shoot at a border between two blocks.

Here is the update method for my Bullet class:

def update(self, dt):
    if self.can_bounce:
        #if the bullet hasnt bounced find its vector using the mousclick pos and player pos
        speed = -10.
        range = 200
        distance = [self.mouse_x - self.player[0], self.mouse_y - self.player[1]]
        norm = math.sqrt(distance[0] ** 2 + distance[1] ** 2)
        direction = [distance[0] / norm, distance[1 ] / norm]
        bullet_vector = [direction[0] * speed, direction[1] * speed]

        self.dx = bullet_vector[0]
        self.dy = bullet_vector[1]

    #check each block for collision
    for block in self.game.solid_blocks:
        last = self.rect.copy()
        if self.rect.colliderect(block):
            topcheck = self.rect.top < block.rect.bottom and self.rect.top > block.rect.top
            bottomcheck = self.rect.bottom > block.rect.top and self.rect.bottom < block.rect.bottom
            rightcheck = self.rect.right > block.rect.left and self.rect.right < block.rect.right 
            leftcheck = self.rect.left < block.rect.right and self.rect.left > block.rect.left
            each test tests if it hit the top bottom left or right side of the block its colliding with 
            if self.can_bounce:                      
                if topcheck: 
                    self.rect = last
                    self.dy  *= -1 
                    self.can_bounce = False
                    print "top"

                if bottomcheck:
                    self.rect = last
                    self.dy  *= -1 #Bottom check
                    self.can_bounce = False
                    print "bottom"

                if rightcheck:
                    self.rect = last 
                    self.dx  *= -1 #right check
                    self.can_bounce = False
                    print "right"

                if leftcheck:
                    self.rect = last
                    self.dx  *= -1 #left check
                    self.can_bounce = False
                    print "left"

            else:
                # if it has already bounced and colliding again kill it
                self.kill()

    for enemy in self.game.enemies_list:
        if self.rect.colliderect(enemy):
            self.kill()
    #update position
    self.rect.x -= self.dx
    self.rect.y -= self.dy

This definitely isn't the best way to do it but I can't think of another way. If anyone has done this or can help that would be awesome!