Python：一个月的第三个星期五

应该这样做：

from datetime import datetimedef is_third_friday(s):    d = datetime.strptime(s, '%b %d, %Y')    return d.weekday() == 4 and 15 <= d.day <= 21

测试：

print is_third_friday('Jan 18, 2013')  # Trueprint is_third_friday('Feb 22, 2013')  # Falseprint is_third_friday('Jun 21, 2013')  # Trueprint is_third_friday('Sep 20, 2013')  # True