Why Python Context Manager is Critical in Every Coding Project

As a coder, it is important for you to be familiar with the python context manager.

Context manager allows coders to allocate and release resources precisely when they want to. The most widely used example of context managers in Python is the 'with' statement. Suppose you have two related operations which you'd like to execute as a pair, with a block of code in between. Context managers allow you to do specifically that.

Managing Resources using context manager :

Suppose a block of code raises an exception or if it has a complex algorithm with multiple return paths, it becomes cumbersome to close a file in all the places.

Generally, in other languages when working with files, try-except-finally is used to ensure that the file resource is closed after usage even if there is an exception. Python provides an easy way to manage resources that is Context Manager. Here the with keyword is used. When it gets evaluated, it should result in an object that performs context management. Context manager can be written using classes or functions (with decorators).

A "resource" here refers to files, network ports, or other finite entities within a "system." When a program needs to access a resource on the computer, for example, it asks the OS for it, and the OS, in turn, provides it with a handle for that resource. Oftentimes, the availability of the said resource is limited; for example, a network port may only be available for one process at any given time, and there may be only so many ports available at that time. It is therefore important to check and make sure that any resource that has been opened is also subsequently closed once finished with it. There are challenges to this, though- if an exception were to occur (i.e., error(s) in the code), the line with the close statement would consequently fail to execute (see below); likewise, if the program were to be forced closed while still executing; if the code has a complex algorithm with multiple return paths, it becomes cumbersome to close a file in all the places; finally, perhaps the most common reason for what's known as resource leak- we just forgot (or didn't know how) to close it. This can cause problems. Leaking resources is not only a source of general inefficiency, but it can leave data vulnerable to potential slowdowns, crashes, and corruption.

Creating a Context Manager

When creating context managers using classes, users need to ensure that the class has the methods: __enter__() and __exit__(). The __enter__() returns the resource that needs to be managed and the __exit__() does not return anything but performs the cleanup operations. Context manager enables the Python user to safely acquire/assign and release resources in the precise way one wishes, often via automatic "setup" and "teardown" mechanisms. While there are unsurprisingly numerous ways to do this in Python, it is most commonly done using the keyword "with." When a statement is executed, the immediately proceeding expression part must be evaluated by a context manager. At its core, a context manager must produce an object that includes and supports two methods: __enter__() and __exit__().

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