Convert input string to snake-, camel-, kebab- or pascalcase.

camelcase.py

from re import findall
from toolz.curried import curry, map, pipe

def to_something_case(text: str, case='snake') -> str:
    """Convert input string to snake-, camel-, kebab- or pascalcase."""
    if not text:
        return text
    first_char, sep, other_first_chars = {
        'snake': (str.lower, '_', str.lower),
        'camel': (str.lower, '', str.title),
        'kebab': (str.lower, '-', str.lower),
        'pascal': (str.title, '', str.title),
    }[case]
    result = pipe(
        text,
        curry(findall)(r'[A-Z][a-z]*|[a-z]+'),
        map(str.lower),
        map(other_first_chars),
        sep.join,
    )
    return first_char(result[0]) + result[1:]


def test_to_something_case():
    """Should convert strings to camelcase."""
    assert to_something_case('My sentence!') == 'my_sentence'
    assert to_something_case('My sentence!', case='snake') == 'my_sentence'
    assert to_something_case('My sentence!', case='camel') == 'mySentence'
    assert to_something_case('My sentence!', case='kebab') == 'my-sentence'
    assert to_something_case('My sentence!', case='pascal') == 'MySentence'
    assert to_something_case('camelCase') == 'camel_case'
    assert to_something_case('PascalCase') == 'pascal_case'