Invalid literal for int error in Python

The Problem

My Python script fails with this error:

ValueError: invalid literal for int() with base 10: ''.

What causes this and how do I fix it?

The Solution

This error message arises from a failure to convert an empty string ('') to an integer. This might arise in the following script if the user presses Enter without providing any input:

user_input = input("Enter a whole number: ")

print(f"Your number is 1 smaller than {1 + int(user_input)}")

To prevent this error, we should check that our string is not empty before passing it to int() for conversion:

user_input = input("Enter a whole number: ")

try:
    print(f"Your number is 1 smaller than {1 + int(user_input)}")
except ValueError:
    print("Please provide a valid number.")

A similar error might arise if the user provides a number with decimal places, such as 1.0. We can avoid this error by converting the string to a float before converting it to an integer:

user_input = input("Enter a whole number (non-whole numbers will be rounded down): ")

try:
    print(f"Your number is 1 smaller than {1 + int(float(user_input))}")
except ValueError:
    print("Please provide a valid number.")