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Python Using With Block To Open Files


There is more than one way to open and close a file. The one we have studied till now is using the open() and close() function. In today's tutorial, we will go through another yet better and straightforward approach of opening and closing files. We will see how we can use, with block to open and close a file, including syntax and benefits. We will be using f as our file’s object.

Opening and closing of files are necessary and crucial steps in file handling. We cannot read, write, or perform any task on a file without opening it first. Everyone is familiar with it because it is the first step in file handling. But what most of us are not familiar with is how vital closing a file is. If we do not close our file after we are done using it, then the file object will keep on consuming processor memory, and also, there will be more chances of exceptions as the file is still open hence, more chances of bugs.

To save ourselves from such situations, we could use a with block to open files.

Now how the with block works?


Its syntax is simple:
With open(“file_name.txt”) as f:

f being the object of the file. The important thing to note is, there is no close() function required. After running the code in the block, the file will automatically be closed.

Now at this level, closing a file does not seem like a big issue, but when we are working on more significant projects with a higher number of files then there are instances where we tend to forget that we have closed our file. In such situations, chances of bugs occurrence increase, and we can not access a file elsewhere until it is closed properly. Also, the program will require more processing power. So, even if we are not dealing with a more significant project now, still closing a file is a good practice because, as a programmer, I can tell you that the practices you adopt now will soon become habits, and they will be difficult to let go.

What opening a file with "With block" actually does is to create a context manager that automatically closes a file after processing it. Another benefit of using a “With block” is that we can open multiple files in a single block by separating them using a comma. All the files could have different modes of opening. For example, we can access one file for reading and another one for writing purposes. Both files should have different objects referring to them.

The syntax would be:
With open(“file1txt”) as f, open(“file2.txt”) as g

Both files will be simultaneously closed together.

Let us once again briefly go over the advantages of With block:



Multiple files can be opened.
The files that are opened together can have different modes.
Automatically closes file.
Saves processing power by opening and closing file only when running code inside the block.
Creates a context manager, so lesser chances of an exception occurring.

Example


with open("harry.txt") as f:
    a = f.readlines()
    print(a)


Conclusion

In this page (written and validated by ) you learned about Python Using With Block To Open Files . What's Next? If you are interested in completing Python tutorial, your next topic will be learning about: Python Scope Global Variables and Global Keyword.



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