Tic-Tac-Toe | Tkinter | Python

import tkinter as tk
from tkinter import messagebox

def btnClicked(button):
    global pturn, turns, turn
    if button["text"] == " " and turns % 2 == 1:
        turns += 1
        button["text"] = "X"
        pturn["text"] = "Waiting on: " + p2.get()
        turn["text"] = "Turn: " + str(turns)
    elif button["text"] == " " and turns % 2 == 0:
        turns += 1
        button["text"] = "O"
        pturn["text"] = "Waiting on: " + p1.get()
        turn["text"] = "Turn: " + str(turns)
    else:
        messagebox.showerror("Error", "That tile has already been chosen!")
    if checkWin == False:
        win()

def win():
    global b1; global b2;  global b3; global b4; global b5; global b6; global b7; global b8; global b9;
    global checkWin, turns
    if b1["text"] == "X" and b2["text"] == "X" and b3["text"] == "X" or b4["text"] == "X" and b5["text"] == "X" and b6["text"] == "X" or b7["text"] == "X" and b8["text"] == "X" and b9["text"] == "X" or b1["text"] == "X" and b4["text"] == "X" and b7["text"] == "X" or b2["text"] == "X" and b5["text"] == "X" and b8["text"] == "X" or b3["text"] == "X" and b6["text"] == "X" and b9["text"] == "X" or b1["text"] == "X" and b5["text"] == "X" and b9["text"] == "X" or b3["text"] == "X" and b5["text"] == "X" and b7["text"] == "X":
        messagebox.showinfo("Win", p1.get() + " has won!")
        checkWin = True
        turns += 1
    elif b1["text"] == "O" and b2["text"] == "O" and b3["text"] == "O" or b4["text"] == "O" and b5["text"] == "O" and b6["text"] == "O" or b7["text"] == "O" and b8["text"] == "O" and b9["text"] == "O" or b1["text"] == "O" and b4["text"] == "O" and b7["text"] == "O" or b2["text"] == "O" and b5["text"] == "O" and b8["text"] == "O" or b3["text"] == "O" and b6["text"] == "O" and b9["text"] == "O" or b1["text"] == "O" and b5["text"] == "O" and b9["text"] == "O" or b3["text"] == "O" and b5["text"] == "O" and b7["text"] == "O":
        messagebox.showinfo("Win", p2.get() + " has won!")
        checkWin = True
        turns += 1
    elif turns == 10:
        turns = 9
        turn["text"] = "Turn: " + str(turns)
        messagebox.showinfo("Draw", "It's a draw!")
        checkWin = True
    if checkWin:
        b1["state"] = "disabled"
        b2["state"] = "disabled"
        b3["state"] = "disabled"
        b4["state"] = "disabled"
        b5["state"] = "disabled"
        b6["state"] = "disabled"
        b7["state"] = "disabled"
        b8["state"] = "disabled"
        b9["state"] = "disabled"

def main():
    global root
    root = tk.Tk()
    root.title("Tic-Tac-Toe")
    tk.Label(text = "Tic-Tac-Toe", bg = "grey47", width = "30", height = "2", font = ("Calibri", 13)).pack()
    tk.Label(text = "").pack()
    tk.Button(text = "Player vs Player", height = "2", width = "30", command = names).pack()
    tk.Label(text = "").pack()
    tk.Button(text = "Player vs Computer",height = "2", width = "30").pack()
    tk.Label(text = "").pack()
    root.mainloop()

def names():
    global names
    names = tk.Toplevel(root)
    names.title("Player Names")
    global p1
    global p2
    p1 = tk.StringVar()
    p2 = tk.StringVar()
    global p1_entry
    global p2_entry
    tk.Label(names, text = "Player 1:", font = ("Calibri", 20)).grid(row = 1, column = 1)
    tk.Entry(names, textvariable = p1, font = ("Calibri", 20)).grid(row = 1, column = 2)
    tk.Label(names, text = "Player 2:", font = ("Calibri", 20)).grid(row = 2, column = 1)
    tk.Entry(names, textvariable = p2, font = ("Calibri", 20)).grid(row = 2, column = 2)
    tk.Button(names, text = "Submit", font = ("Calibri", 13), command = verifynames).grid(row = 3, column = 2, sticky = tk.E)

def verifynames():
    if p1.get() == "" or p2.get() == "":
        messagebox.showerror("Error", "Don't leave any spaces!")
    else:
        pvp()

def pvp():
    names.destroy()
    w = 8
    h = 4
    pvp = tk.Toplevel(root)
    pvp.title("Tic-Tac-Toe")
    global pturn, turns, turn, checkWin
    pturn = tk.Label(pvp, text = "Waiting on: " + p1.get(), font = ("Calibri", 28))
    turns = 1
    turn = tk.Label(pvp, text = "Turn: " + str(turns), font = ("Calibri", 28))
    checkWin = False
    pturn.grid(row = 1, column = 1, columnspan = 2, sticky = tk.W)
    turn.grid(row = 1, column = 3, sticky = tk.E)
    global b1; global b2;  global b3; global b4; global b5; global b6; global b7; global b8; global b9;
    b1 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b1))
    b1.grid(row = 2, column = 1)
    b2 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b2))
    b2.grid(row = 2, column = 2)
    b3 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b3))
    b3.grid(row = 2, column = 3)
    b4 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b4))
    b4.grid(row = 3, column = 1)
    b5 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b5))
    b5.grid(row = 3, column = 2)
    b6 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b6))
    b6.grid(row = 3, column = 3)
    b7 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b7))
    b7.grid(row = 4, column = 1)
    b8 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b8))
    b8.grid(row = 4, column = 2)
    b9 = tk.Button(pvp, text = " ", font = ("Calibri", 32), bg = "grey47", width = w, height = h, command = lambda: btnClicked(b9))
    b9.grid(row = 4, column = 3)

main()