connect4 in python (bad code)

connect4.py

board = [[0, 0, 0, 0, 0, 0, 0],
         [0, 0, 0, 0, 0, 0, 0],
         [0, 0, 0, 0, 0, 0, 0],
         [0, 0, 0, 0, 0, 0, 0],
         [0, 0, 0, 0, 0, 0, 0],
         [0, 0, 0, 0, 0, 0, 0]]
turn = 1
temp = False

def ask():
    global turn
    if turn == 1:
        line = int(input(f'\u001b[33mplayer {turn}\u001b[0m\nline: ')) - 1
    else:
        line = int(input(f'\u001b[31mplayer {turn}\u001b[0m\nline: ')) - 1
    a = 5
    if not board[0][line] == 0:
        print(f'line {line + 1} is full')
        visualize()
        ask()
    for _ in range(6):
        if board[a][line] == 0:
            board[a][line] = turn
            break
        else:
            a -= 1
            continue
    a = find(line, a)
    tie = checktie()
    if tie:
        print('\u001b[32mtie!\u001b[0m')
        exit()
    if not a:
        visualize()

    if turn == 1:
        turn = 2
    else:
        turn = 1
    ask()

def find(line, a):
    h = findhorizontal(line, a)
    if h[0] >= 4:
        visualize(h[1])
        win()
        return True
    v = findvertical(line, a)
    if v[0] >= 4:
        visualize(v[1])
        win()
        return True
    s = findslash(line, a)
    if s[0] >= 4:
        visualize(s[1])
        win()
        return True
    bs = findbackslash(line, a)
    if bs[0] >= 4:
        visualize(bs[1])
        win()
        return True

def findhorizontal(line, a):
    n = 1
    p = [[a, line]]
    # west
    for _ in range(1, 5):
        t = line - _
        if t < 0:
            break
        if board[a][t] == turn:
            p.append([a, t])
            n += 1
        else:
            break
    # east
    for _ in range(1, 5):
        t = line + _
        if t > 6:
            break
        if board[a][t] == turn:
            p.append([a, t])
            n += 1
        else:
            break
    return n, p

def findvertical(line, a):
    n = 1
    p = [[a, line]]
    # south
    for _ in range(1, 5):
        t = a + _
        if t > 5:
            break
        if board[t][line] == turn:
            p.append([t, line])
            n += 1
        else:
            break
    return n, p

def findslash(line, a):
    n = 1
    p = [[a, line]]
    # southwest
    for _ in range(1, 5):
        t = a + _
        t1 = line - _
        if t > 5:
            break
        if t1 < 0:
            break
        if board[t][t1] == turn:
            p.append([t, t1])
            n += 1
        else:
            break
    # northeast
    for _ in range(1, 5):
        t = a - _
        t1 = line + _
        if t < 0:
            break
        if t1 > 6:
            break
        if board[t][t1] == turn:
            p.append([t, t1])
            n += 1
        else:
            break
    return n, p

def findbackslash(line, a):
    n = 1
    p = [[a, line]]
    # northwest
    for _ in range(1, 5):
        t = a - _
        t1 = line - _
        if t < 0:
            break
        if t1 < 0:
            break
        if board[t][t1] == turn:
            p.append([t, t1])
            n += 1
        else:
            break
    # southeast
    for _ in range(1, 5):
        t = a + _
        t1 = line + _
        if t > 5:
            break
        if t1 > 6:
            break
        if board[t][t1] == turn:
            p.append([t, t1])
            n += 1
        else:
            break
    return n, p

def win():
    # print(board)

    if turn == 1:
        print(f'\u001b[33mplayer {turn} wins!\u001b[0m\n')
    else:
        print(f'\u001b[31mplayer {turn} wins!\u001b[0m\n')
    exit()

def visualize(p = None):
    global board
    a = ''
    b = ''
    c = ''
    d = ''
    e = ''
    f = ''

    if not p == None:
        for _ in p:
            board[_[0]][_[1]] = 3

    for _ in board[0]:
        a += str(_) + ' '

    for _ in board[1]:
        b += str(_) + ' '

    for _ in board[2]:
        c += str(_) + ' '

    for _ in board[3]:
        d += str(_) + ' '

    for _ in board[4]:
        e += str(_) + ' '

    for _ in board[5]:
        f += str(_) + ' '

    a = a.replace('0', '⬤')
    b = b.replace('0', '⬤')
    c = c.replace('0', '⬤')
    d = d.replace('0', '⬤')
    e = e.replace('0', '⬤')
    f = f.replace('0', '⬤')

    if not p == None:
        a = a.replace('3', '\u001b[35m⬤\u001b[0m')
        b = b.replace('3', '\u001b[35m⬤\u001b[0m')
        c = c.replace('3', '\u001b[35m⬤\u001b[0m')
        d = d.replace('3', '\u001b[35m⬤\u001b[0m')
        e = e.replace('3', '\u001b[35m⬤\u001b[0m')
        f = f.replace('3', '\u001b[35m⬤\u001b[0m')

    a = a.replace('1', '\u001b[33m⬤\u001b[0m')
    b = b.replace('1', '\u001b[33m⬤\u001b[0m')
    c = c.replace('1', '\u001b[33m⬤\u001b[0m')
    d = d.replace('1', '\u001b[33m⬤\u001b[0m')
    e = e.replace('1', '\u001b[33m⬤\u001b[0m')
    f = f.replace('1', '\u001b[33m⬤\u001b[0m')

    a = a.replace('2', '\u001b[31m⬤\u001b[0m')
    b = b.replace('2', '\u001b[31m⬤\u001b[0m')
    c = c.replace('2', '\u001b[31m⬤\u001b[0m')
    d = d.replace('2', '\u001b[31m⬤\u001b[0m')
    e = e.replace('2', '\u001b[31m⬤\u001b[0m')
    f = f.replace('2', '\u001b[31m⬤\u001b[0m')

    print(f'{a}\n{b}\n{c}\n{d}\n{e}\n{f}\n')

def checktie():
    c = True
    for a in board:
        for _ in a:
            if _ == 0:
                c = False
                break
    return c

visualize()
ask()