Look at the parts of that program and where each idea came from:

Part	Course unit
`Expense` data class	33, Type hints and dataclasses
Splitting and stripping lines	11, Strings in depth
Validating dates with `strptime`	19, The standard library
Raising `ValueError`	17, Errors and exceptions
The `Ledger` class	21, Classes and objects
Totals by category	13, Dictionaries
Sorting by total, then name	25, Sorting algorithms
Aligned columns	11, Formatting output
Saving as JSON	38, Working with data
Small functions, one job each	39, Writing clean code

That is a real program. Add a command loop (Unit 13's contact book shows how) and you could use it every day.