Except vs. except for

Except vs. except for用法的差別，雖然很用力的請教google大神，但還是沒有很確定的答案，先跟大家分享一下目前覺得比較make sense的分別方式，如果有更好的解釋，歡迎大家提供囉：

(1) except/except for (整體裡除了....)
     Everyone was invited to the party except (for) Mary.

(2) except for (were it not for)
     I would have arrived the restaurant on time except for the busy traffic.


Additional note:
以上只是except一部分的用法，其他部分需要另外查詢字典囉。