import re


def get_life_range(source):
    """
    Return the birth and death year from _source (as a tuple).

    Return empty strings if not available.
    """
    years = []
    for event in ["from", "to"]:
        if source["lifespan"].get(event):
            date = source["lifespan"][event].get("date", "")
            if date:
                date = date.get("comment", "")
            if "-" in date and not re.search("[a-zA-Z]", date):
                year = date[:date.find("-")]
            else:
                year = date
        else:
            year = ""
        years.append(year)

    return years[0], years[1]