Age calculator in python
Generally, it is often not a good idea to hardcode values. For example, take a look at this piece of code. It won't work correctly from 2021 onwards:
if input_year &lt;= 0 or input_year &gt; 2020:
    print(&quot;don't you know your birthday??&quot;)

Better do it like this:
date = datetime.now()
current_year = int(date.year)

if input_year &lt;= 0 or input_year &gt; current_year:
    print(&quot;don't you know your birthday??&quot;)

This will make your program work in future years without the need to change the value for the current year manually.