The reptile single-threaded asynchronous multi-task coroutine +

<h3> + single-threaded asynchronous multi-task coroutine </ h3> 

- meaning: to enhance the efficiency of data crawling - crawling asynchronous way - multi-threaded / multi-process (not recommended) 
    - Pool (suitable) 
    - Multi-threaded + asynchronous task coroutine (recommended) 
- concept 
    - coroutines: coroutine object. Can be defined using the async keyword modified (special function) of a function, when the special function is called, you can return a coroutine object. When the function is called, the internal function implementation statement will not be executed immediately. 
        - == coroutine special functions 
    - the task objects: 
        - to essentially coroutine further encapsulated objects. 
            - == task object of special functions 
        - a task object to bind a callback 
            - add_done_callback (callback) 

    - event loop (EventLoop): infinite loop target 
        - we have to be registered to the event loop task object object, and then open the event loop object. 
        - event loop object when the object is to perform tasks based on asynchronous 

    - await the async 

    - Note: 
        - ensure internal special function does not appear to support asynchronous modules corresponding to the code 
        - experience blocking operations must await keyword inside special functions suspend its manual
        - If you want to register multiple tasks objects to the event loop, you must object encapsulates multiple tasks to a list and the list of registered (must use the wait method to carry out the task object list pending) to the event loop 


- aiohttp modules: a module supports asynchronous network requests 
    - pip install aiohttp