python: resize image to max

import imghdr, os
from PIL import Image

directory = 'C:\Users\UserBob\Desktop\RANDOM\0'

# recursively resize images with python
for image in os.listdir('.'):
    fp = image
    try:
        # if file is image
        if imghdr.what(fp) is not None:
            with open('fn','a+') as f:
                f.write(fp+'\n')
            im = Image.open(fp)
            if (im.size[0] < 3000) or (im.size[1] < 3000):
                #find the coeffecient to scale smallest edge to 550
                width = 3000 / float(im.size[0])
                height = 3000 / float(im.size[1])
                ratio = min(width, height)
                width = int(float(im.size[0]) * ratio)
                height = int(float(im.size[1]) * ratio)
                #NEAREST for upsizing, antialias for downsizing
                resized_image = im.resize((width, height), Image.NEAREST)
                resized_image.save(fp, format='JPEG')
    except Exception, e:
        import traceback;print(traceback.format_exc())
        print(e)