4.7 String tests

What does this function do?

def validate(name):
    if name:
        if name[0] != '_' and not name[0].isalpha():
            return False
        for character in name[1:]:
            if character != '_' and not character.isalnum():
                return False
        return True
    return False

Empty names are not good.

validate("")

False

Names that have a single underscore are okay.

validate("_")

True

Names that are digits and letters can be good. These are “alphanumeric.”

validate("income2021")

True

Names that contain underscores and alphanumeric characters can be good.

validate("income_2021")

True

Names that contain other characters are bad.

validate("income-2021")

False

Names that start with a digit are bad.

validate("2021_income&quot...