1. Indexable, not sliceable
2. Can be deleted
3. Non-sequential complete loop (for)
4.for a in b(.keys)、 for a in b.values、for a,b in c.items()
1. Indexable, not sliceable
2. Can be deleted
3. Non-sequential complete loop (for)
4.for a in b(.keys)、 for a in b.values、for a,b in c.items()