Constructing a Czech adverb from an adjective

Question

I am looking for an algorithm to create Czech adverbs when given an adjective. I was looking for a decent set of rules, but I was not able to find anything comprehensive. Going from example words I have the following rules - in Python code, but it should be easy to understand even for nonprogrammers. So for example if a word ends with "lý", the last character is replaced with an e (resulting in "le").

def adjective_to_adverb(word: str) -> str:
    if word.endswith("lý") or word.endswith("sý"):
        return word[:-1] + "e"
    elif word.endswith("rý"):
        return word[:-2] + "ře"
    elif word.endswith("í"):
        return word[:-1] + "ě"
    elif word.endswith("cký"):
        return word[:-2] + "ky"
    elif word.endswith("ký"):
        return word[:-2] + "ce"
    elif word.endswith("ý"):
        return word[:-1] + "ě"
    else:
        raise ValueError(f"Adjective {word} does not end in a known suffix")

I think my rules are incomplete. What other cases would I need to handle?

Answer 1

I (hopefully) found some more rules, they are here.

def adjective_to_adverb(word: str) -> str:
    if word.endswith("lý") or word.endswith("sý"):
        return word[:-1] + "e"
    elif word.endswith("rý"):
        return word[:-2] + "ře"
    elif word.endswith("cí"): # Mostly these adverbs don't exist though
        return word[:-1] + "e"
    elif word.endswith("í"):
        return word[:-1] + "ě"
    elif word.endswith("chý"):
        return word[:-3] + "še"
    elif word.endswith("cký") or word.endswith("ský"):
        return word[:-2] + "ky"
    elif word.endswith("hý"):
        return word[:-2] + "ze"
    elif word.endswith("ký"):
        return word[:-2] + "ce"
    elif word.endswith("ý"):
        return word[:-1] + "ě"
    else:
        raise ValueError(f"Adjective {word} does not end in a known suffix")

Edit: Thanks a lot to Vladimir for finding what was missing, I now added it.

Answer 2

A cleaner way to implement the same logic:

def adjective_to_adverb(word: str) -> str:
    suffix_mapping = {
        "lý": "le",
        "sý": "se",
        "rý": "ře",
        "cí": "ce",  # Mostly these adverbs don't exist though
        "í": "ě",
        "chý": "še",
        "cký": "cky",
        "ský": "sky",
        "hý": "ze",
        "ký": "ce",
        "ý": "ě"
    }

    for suffix, replacement in suffix_mapping.items():
        if word.endswith(suffix):
            return word[:-len(suffix)] + replacement

    raise ValueError(f"Adjective {word} does not end in a known suffix")