Day 4: Practiced regular expressions. They're used to search for specific parts of text based on some elements the user provides. Regular expressions can shorten code - especially code that require verifying the right input. Also learnt about input validation - the author has created his own library of functions similar to the input() function. However, these functions have various added functionalities.
One thing I learnt from this is to find out libraries related to the task I want to write code on. It can save me time and make me use less effort - rather than having to figure how to produce the script entirely on my own.