wondering what happened to my python code that draw a checkerboard with turtle? any helps?

import turtle
def main():
    turtle.pensize(4)
    for x in range(5):
        for y in range(5):
            turtle.penup()
            turtle.goto(x*50,y*50)
            turtle.pendown()
            if (x+y)%2 == 0:
                turtle.begin_fill()
                black_square(50)
                turtle.end_fill()
            else:
                turtle.begin_fill()
                white_square(50)
                turtle.end_fill()

def black_square(width):
    turtle.fillcolor('black')
    for x in range(4):
        turtle.forward(width)
        turtle.left(90)

def white_square(width):
    turtle.fillcolor('white')
    for x in range(4):
        turtle.forward(width)
        turtle.right(90)

main()

Current image:

Intended image:

My code won’t draw a correct checkerboard pattern, but I wonder why every for loop my square black and white both executed at the same time? I am not asking for the correct code that will get me the correct checkerboard and I just want an explanation for the mistakes in my code.

Answer

I don’t know how to explain your mistakes without giving you the correct code, but I will try:

basically the mistake is that black_square and white_square are drawing squares at the same location. The starting point is 50 units apart, but because the squares are drawn in opposite directions (clockwise and counter-clockwise), the resulting area overlaps. black_square would draw a square below the starting point, while white_square would draw a square above its starting point.