Invalid literal for int() with base 10: ''

mod = int(num)%2

While I issue this command in python 3, am getting the following error, Please help!!
Traceback (most recent call last):
File “<pyshell#52>”, line 1, in
mod = int(num)%2
ValueError: invalid literal for int() with base 10: ‘’

empty strings ('') can’t be converted to integers, thus you get an error