Card Game old Gcse Python Code

import random
####################################################
def deck_creation():
  colours = ["red","black","yellow"]
  deck = []
  b=-10
  for i in range(3):
    b+=10
    for a in range(10):
      deck.append([])
      deck[(a+b)].append(a+1)
      deck[(a+b)].append(colours[i])
  random.shuffle(deck)
  return (deck)
####################################################
creds = [["a","a"], ["james", "the"], ["mat", "dog"]]
a=0
while a < 1:
    print("")
    user=input("Enter Your Username:")
    pas=input("Enter Your Password:")
    for item in creds:
      if item[0] == user and item[1]==pas:
        print ("__________________________login successfull!__________________________")
        deck = deck_creation()
        a=+1
      else: print ("------", end="")
####################################################
player1 =[]
player2 =[]
for i in range(15):
  player1.append(deck[0])
  player2.append(deck[1])
  deck.remove(deck[0])
  deck.remove(deck[0])
####################################################
def p1w():
  print ("Player1 Won!")
  print ("player1 cards=", player1[0], "player2 cards=", player2[0])
  player1_wins.append(player1[0])
  player1_wins.append(player2[0])
  player1.remove(player1[0])
  player2.remove(player2[0])
def p2w():
  print ("Player2 Won!")
  print ("player1 cards=", player1[0], "player2 cards=", player2[0])
  player2_wins.append(player1[0])
  player1_wins.append(player2[0])
  player2.remove(player2[0])
  player1.remove(player1[0])
####################################################
player1_wins=[]
player2_wins=[]
for i in range(15):
  if player1[0][1] == player2[0][1]:
    if player1[0][0] > player2[0][0]:p1w()
    else:p2w()
  elif player1[0][1] == "red" and player2[0][1]== "black": p1w()
  elif player2[0][1] == "red" and player1[0][1]== "black": p2w()
  elif player1[0][1] == "yellow" and player2[0][1]== "red": p1w()
  elif player2[0][1] == "yellow" and player1[0][1]== "red": p2w()
  elif player1[0][1] == "black" and player2[0][1]== "yellow": p1w()
  elif player2[0][1] == "black" and player1[0][1]== "yellow": p2w()
print ("-------------------------------------------------------------------------")
print ("player1 wins = ", player1_wins, "   TOTAL =", len(player1_wins))
print ("")
print ("player2 wins = ", player2_wins, "   TOTAL =", len(player2_wins))
print ("")
if (len(player1_wins))>(len(player2_wins)): print ("OVERALL Player1 WINS")
else: print ("OVERALL Player2 WINS")