Player gets stuck in wall pygame

Question

Whenever the player collides with the wall, they just get stuck in the wall and can't move. Here's the code:

collide = pg.sprite.collide_mask(self, self.game.map)

        if keys[pg.K_w]:
            self.pos.y -= playerSpeed
            if collide:
                self.pos.y += playerSpeed
        if keys[pg.K_a]:
            self.pos.x -= playerSpeed
            if collide:
                self.pos.x += playerSpeed
        if keys[pg.K_s]:
            self.pos.y += playerSpeed
            if collide:
                self.pos.y -= playerSpeed
        if keys[pg.K_d]:
            self.pos.x += playerSpeed
            if collide:
                self.pos.x -= playerSpeed

Answer 1

Well that is exactly what your code tells:

collide = pg.sprite.collide_mask(self, self.game.map)

so this will be true when the player hits the wall

if keys[pg.K_s]:
    self.pos.y += playerSpeed
    if collide:
        self.pos.y -= playerSpeed

so if collide is true, what effectively happens is:

self.pos.y += playerSpeed
self.pos.y -= playerSpeed

So the net result is that the position does not change (same for all other directions).

The real question is now: what would you like to happen? Probably you should know which of the four directions is blocked by the wall, and only set the movement in that direction to 0.

Answer 2

The issue is that you need to check for collisions before the player gets stuck on the object. Once the player is in a collision state, the test:

collide = pg.sprite.collide_mask(self, self.game.map)

Will simply return True no matter what. As @ChrisMaes points out, once collided, the movement will never again effect the outcome.

The solution is to test the collision before the movement is finalised:

if keys[pg.K_w]:
    self.pos.y -= playerSpeed
    if ( pg.sprite.collide_mask( self, self.game.map ) ):
        self.pos.y += playerSpeed                          # Undo the movement
# ... etc, same change for the rest of the movement keys

There is a problem with this method though. If playerSpeed is say a constant of 5, it would be impossible for the player to move to be resting against a barrier, since the test is done at 5 pixels, they get stopped at 1-5 pixels away. If the player speed is fixed (and > 1), it would be necessary to determine how much the player could have moved up-to the barrier, and only allow movement of that distance. This leaves the player right-next to the thing it collided with, rather than 1-4 pixels away.