Remove "()" after callback:
myftp.storbinary(..., callback=UploadTracker)
from ftplib import FTP def UploadTracker(): print("HELLO") myftp = FTP() myftp.connect(host='mysite.com') myftp.login('me','mypw') myftp.storbinary('STOR mydata.txt', open('mydata.txt', 'rb'), callback=UploadTracker) myftp.quit()