def _iso_num_weeks(iso_year):
    "Get the number of ISO-weeks in this year"
    year_start = _iso_year_start(iso_year)
    next_year_start = _iso_year_start(iso_year+1)
    year_num_weeks = ((next_year_start - year_start).days) // 7
    return year_num_weeks
Get the number of ISO-weeks in this year