The error message invalid literal for int() with base 10 would seem to indicate that you are passing a string that's not an integer to the int() function . In other words it's either empty, or has a character in it other than a digit.
You can solve this error by using Python isdigit() method to check whether the value is number or not. The returns True if all the characters are digits, otherwise False .
The other way to overcome this issue is to wrap your code inside a Python try...except block to handle this error.
Python2.x and Python3.x
Sometimes the difference between Python2.x and Python3.x that leads to this ValueError: invalid literal for int() with base 10 .
With Python2.x , int(str(3/2)) gives you "1". With Python3.x , the same gives you ("1.5"): ValueError: invalid literal for int() with base 10: "1.5".