我想要避免嵌套循环和加速循环

代码如下

for x in xFolders:
    print(str(level) + "/" + x)
    yFiles = os.listdir(str(level) + "/" + x)
    print(yFiles)
    x1Up = str(int(int(x) / 2))
    if not os.path.exists(str(level-1) + "/" + x1Up):
        os.makedirs(str(level-1) + "/" + x1Up)
    for yFile in yFiles:
        y = yFile.split(".")[0]

        y1Up = str(int(int(y) / 2))

        im = Image.open(str(level) + "/" + x + "/" + yFile)
        im.thumbnail((128,128))

        parent = None

        try:
            parent = Image.open(str(level - 1) + "/" + x1Up + "/" + y1Up + ".png")
        except:
            parent = Image.new("RGBA", (256, 256), (256, 0, 256, 256))
        xOffset = 0
        yOffset = 0
        if int(x) & 1:
            xOffset = 128

        if int(y) & 1:
            yOffset = 128

        parent.paste(im, (xOffset, yOffset, xOffset + 128, yOffset + 128))

        parent.save(str(level - 1) + "/" + x1Up + "/" + y1Up + ".png")

问题来源StackOverflow 地址：/questions/59385467/i-want-want-to-avoid-nested-loop-and-speed-up-the-loop