Iterate objects and iterator objects in Python

Just learning Python, the individual understanding of "iterative objects" and "iterator objects" doesn't know right.

1. Several concepts

1. Iterative tools: Includes for loop, list resolution, in membership test ..... And so on, to access the actions (?) of the elements in an iterative object (container) in turn.

2. Iterator object: An object with the __next__ () method. The method can automatically return the next result, and when the end of the sequence is reached, the stopiteration exception is thrown.

3. Iterative object: An object with the __iter__ () method. The method can get its iterator object.

2. Iterative process (for example for loop)

For loop start: Automatically invokes the __iter__ () method of an iterative object to get its iterator object (containing the next method)

For loop: Automatically invokes the __next__ () method of an Iterator object to get the next element

For Loop end: When the __next__ () call throws a Stopiteration exception, the loop ends.

3. A few notes

(1) An Iterator object can also be an iterator object, such as a file object. At this point, you can iterate over the object itself with the __next__ () method, and its __iter__ () method returns its own

(2) For many built-in objects and their derived objects, such as list, dict, etc., because they need to support opening iterators multiple times, so they are not iterator objects, they need to return their iterator objects with the __iter__ () method and use the iterator object to access the other elements.

Iterate objects and iterator objects in Python