This error message means that the string supplied to int cannot be parsed as an integer. The last part after : displays the provided string.

In the case of the problem description, the input is an empty string , written as ''.

Here's another example - strings representing floating point values ??cannot be converted directly with int:

>>> int('55063.000000')
Traceback (most recent call last):
  File "", line 1, in 
ValueError: invalid literal for int() with base 10: '55063.000000'

Instead, first convert to float:

>>> int(float('55063.000000'))
55063