(coding to get) Python code completion to choose from a list of allowable strings

Question

Assume a simple function:

def example(formula="")
    ...

Where the argument "formula" should be one of 2400 possible chemical formulas. Would there be a way to get code completion for choosing one string from a list of 2400 strings?

First idea was to chose from a list of class attributes. However, I can not use the dir() method. These formula strings are often invalid for use as attribute names.

I don't see another method that would list a choice without using attributes of something.

Thanks

Answer 1

Use enums, which PyCharm for instance code completes just nicely, especially if you use type hinting.

import enum

class ChemFormula(enum.Enum):
    Chlorine = "cl2"
    Hydrogen = "h2"
    Water = "h2o"


def example(formula: ChemFormula) -> None:
    ....