def extract_subs_value(text):
    """Extract a subsitution value from a line of text.

    This is just a friendly function to grab a float value for Ks and Kn
    values from the junk I get from the last line of the yn00 file.

    Line:
    2    1    52.7   193.3   2.0452  0.8979  0.0193 0.0573 +- 0.0177
    2.9732 +- 3.2002

    Parts:
        ['   2    1    52.7   193.3   2.0452  0.8979  0.0193 0.0573',
         ' 0.0177  2.9732', ' 3.2002\n']

    So we want 0.0573 for Kn and 2.9732 for Ks.
    """
    parts = text.split()
    value = float(parts[-1])

    return value