Median filter in python 🐍

median-filter.py

from PIL import Image
path = "noise.png" # Your image path 
img = Image.open(path)
members = [(0,0)] * 9
newimg = Image.new("RGB",(width,height),"white")
for i in range(1,width-1):
    for j in range(1,height-1):
        members[0] = img.getpixel((i-1,j-1))
        members[1] = img.getpixel((i-1,j))
        members[2] = img.getpixel((i-1,j+1))
        members[3] = img.getpixel((i,j-1))
        members[4] = img.getpixel((i,j))
        members[5] = img.getpixel((i,j+1))
        members[6] = img.getpixel((i+1,j-1))
        members[7] = img.getpixel((i+1,j))
        members[8] = img.getpixel((i+1,j+1))
        members.sort()
        newimg.putpixel((i,j),(members[4]))

width and height are not defined in your code
you need to add

img = Image.open(path)
width, height=img.size