Python with usage

In Python, the WITH keyword is a good thing to manage to implement context protocol objects for you. For example: file, and so on. Examples are as follows:

From __future__ import with_statement with open (' Cardlog.txt ', ' r ') as item: For line in   item:     

At the end of file, it automatically closes the handle.

In python2.6, with formally became the keyword
So before python2.5, to use with, you need to use:

It has the following principles:
All objects that implement the context protocol contain the following three methods:
__CONTEXT__ () it returns a self-managed context object, or a really meaningful context manager

__enter () __ enters the context manager and begins the iteration

When the With statement ends, either the normal end or the exception is thrown, the __exit__ () is executed, which is used to close the resource connection.

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