python - Partial Collision Error -

i trying make version of pong using pygame, having issues detecting collision between ball , paddle. got detection working both paddles, came realize left player cannot move paddle when ball collides without ball passing through. player on right has no such issue, , keeping left player still allows ball reflect normally.

import pygame, sys pygame.locals import *  pygame.init() pygame.mixer.init() pygame.font.init()  black = (0, 0, 0) white = (255, 255, 255)  screenx = 1080 screeny = 720  clock = pygame.time.clock() pygame.mouse.get_pos in (screenx, screeny):     pygame.mouse.set_visible(false)   # blueprint creating player character class player:     # defines initial conditions player     def __init__(self):         self.xpos = 0         self.ypos = 0         self.width = 20         self.length = 100         self.speed = 10         self.move = 0         self.upkey = 0         self.downkey = 0         self.score = 0         self.rect = pygame.rect((self.xpos, self.ypos, self.width, self.length))      # if player character, defines paddle movement     def player_move(self, key):         if key[self.upkey]:             self.ypos -= self.speed             self.move = -1         elif key[self.downkey]:             self.ypos += self.speed             self.move = 1         else:             self.move = 0      # creates screen boundary players     def player_boundary(self, key):         if self.ypos == 0:             self.speed = 0             self.move = 0             if key[self.downkey]:                 self.speed = 10                 self.move = -1         elif self.ypos + self.length == screeny:             self.speed = 0             self.move = 0             if key[self.upkey]:                 self.speed = 10                 self.move = 1      # draws player rectangle surface     def draw(self, surface):         self.rect = pygame.draw.rect(surface, white, (self.xpos, self.ypos, self.width, self.length))   # blueprint creating ball class ball:     def __init__(self):         self.size = 15         self.speed = 10         self.vy = 0         self.vx = 10         self.ypos = screeny/2         self.xpos = 100         self.rect = pygame.rect((self.xpos, self.ypos, self.size, self.size))      # defines movement of ball (in xy components)     def ball_move(self):         self.ypos += self.vy         self.xpos += self.vx      # method ball bouncing off of player paddle **     def ball_block(self, player):         if player.move > 0:             self.vy += player.speed * 0.3             self.vx = -((self.speed**2 - self.vy**2) ** .5)         elif player.move < 0:             self.vy = player.speed * -0.3             self.vx = -((self.speed**2 - self.vy**2) ** .5)         elif player.move == 0:             self.vx = -self.vx      # reflecting off of screen boundaries **     def ball_reflect(self, screeny):         if self.ypos == 0:             self.vy = -self.vy         elif self.ypos == screeny - self.size:             self.vy = -self.vy      # method detecting when player has scored     def score(self):         if self.xpos == 0:             self.vx = -self.vx             print ('score')         elif self.xpos == screenx - self.size:             self.vx = -self.vx             print ('score')      # draws ball surface     def draw(self, surface):         self.rect = pygame.draw.rect(surface, white, (self.xpos, self.ypos,     self.size, self.size))  def setup():     # assigns values player 1 (left side)     player1 = player()     player1.xpos = 50     player1.ypos = screeny/1.5     player1.upkey = k_w     player1.downkey = k_s      # assigns values player 2 (right side)     player2 = player()     player2.xpos = screenx - player2.width - 50     player2.ypos = screeny/1.5     player2.upkey = k_up     player2.downkey = k_down      return player1, player2  # main loop of game def main():     player1, player2 = setup()     ball = ball()     play = true      while play:         event in pygame.event.get():             if event.type == quit:                 pygame.quit()                 sys.exit()          key = pygame.key.get_pressed()         if key[k_escape]:             play = false          if ball.rect.colliderect(player1):  # reason, ball can go through p1 while moving             ball.ball_block(player1)         elif ball.rect.colliderect(player2):             ball.ball_block(player2)          # had issue ball going through bottom, fixed adding screeny dependencies         if ball.ypos == 0:             ball.ball_reflect(screeny)         elif ball.ypos == screeny - ball.size:             ball.ball_reflect(screeny)          player1.player_move(key)         player2.player_move(key)         ball.ball_move()          # calls methods player boundaries , ball scoring         player1.player_boundary(key)         player2.player_boundary(key)         ball.score()  # ball score if colliding head on , not on p2's side          # draws objects screen         surface.fill(black)         player1.draw(surface)         player2.draw(surface)         ball.draw(surface)          pygame.display.update()         clock.tick(60)  # sets screen, calls main loop surface = pygame.display.set_mode((screenx, screeny)) pygame.display.set_caption('pong')  main() 

as far can tell, code both players identical, , yet 1 player works in way intended to. appreciated, , thank time.

edit: fixed adding few lines ball_block method

    def ball_block(self, player):     if player.move > 0:         self.vy += player.speed * 0.3         if self.vx < 0:             self.vx = ((self.speed**2 - self.vy**2) ** .5)         elif self.vx > 0:             self.vx = -((self.speed**2 - self.vy**2) ** .5)     elif player.move < 0:         self.vy = player.speed * -0.3         if self.vx < 0:             self.vx = ((self.speed**2 - self.vy**2) ** .5)         elif self.vx > 0:             self.vx = -((self.speed**2 - self.vy**2) ** .5)     elif player.move == 0:         self.vx = -self.vx 

if player moving during collision, setting

self.vx = -((self.speed**2 - self.vy**2) ** .5) 

so it's negative