python ---- fundamental iteration

1. those in python can use for loops, and those can traverse？
   答：iterable objects or objects that umplenment iterator protocols can be traversed
   probably include： dictionary，list，string，file，tuple
   2.it’s wrong to ttraverse the dictionary table like this
   
   
2. all objects that can be iterated are due to the existence of a next function, which is used in the follwing ways
3. 
4. instead of using f.readlines() to iterate in actual development, use f directly or new method , which takes up less internal memory
5. 
6. what objects can be iterated?
   an object that contains the next method is an iterative object
7. to determine whether an object uses a method,use is an follows
8. 
9. objects paid by files can only be used once
   10.
10. add iters method to urls,which can be used to implement next() function
11. 
12. summary
    15.
13. making elements capitalized or filtering certain elements
14. 
15. other silly ways
16. example of map() and zip()
17. 
18. summary