Q:

when asyncio.StreamReader.read() called, which type of Error occur? 

Now I make TCP server with asyncio. 
I want added exception error handling in my code. ( like below)
    try:
        data = await reader.read(SERVER_IO_BUFFER_SIZE)
    except SomeError:
        #error handle

So, I look asyncio official document. 
but I can't find any of information about Errors that may occur. 
(link: https://docs.python.org/3/library/asyncio-stream.html#asyncio.StreamReader.read)
How can I get infomation about Errors that may occur? 

A:

The exact errors that may occur will depend on the type of the stream behind the StreamReader.  An implementation that talks to a socket will raise IOError, while an implementation that reads data from a database might raise some database-specific errors. 
If you are dealing with the network, e.g. through asyncio.open_connection or asyncio.start_server, you can expect instances of IOError and its subclasses.  In other words, use except IOError as e.
Also, if the coroutine is cancelled, you can get asyncio. CancelledError at any await.  You probably don't want to handle that exception - just let it propagate, and be sure to use the appropriate finally clauses or with context managers to ensure cleanup. ( This last part is a good idea regardless of CancelledError.)