def upar(unit_st):
    """Parse unit_st into num (float), unit (string) pair"""
    unit_st = str(unit_st)
    try:
        ind = list(map(str.isalpha, unit_st)).index(True)
        num, unit = float(unit_st[:ind]), unit_st[ind:]
    except ValueError:
        num = float(unit_st)
        unit = 'u'
    return num, unit
