Python reading a file line by line

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Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Linked Related Hot Network Questions. Question feed. Stack Overflow works best with JavaScript enabled. Accept all cookies Customize settings. With the in keyword, we can loop through the lines of the file. Unfortunately, this solution will not work for our client.

File management is a delicate procedure in any programming language. Files must be handled with care to prevent their corruption. When a file is opened, care must be taken to ensure the resource is later closed. And there is a limit to how many files can be opened at once in Python. In order to avoid these problems, Python provides us with the Context Manager.

A method like readlines will work okay for small files, but what if we have a more complex document? Using Python with statements will ensure that files are handled safely. We are eager to address any concerns you may have about our products. We want to make sure that you are completely satisfied with your purchase. The additional advantage of the function is that it does not read the iterator until the end.

So you can do more complex things:. HOW TO? ID : viewed : 9 Tags : python file line python Top 5 Answer for python - How to read specific lines from a file by line number? In Python 2. To Conclude: Use fileobject. Use linecache for a more elegant solution, which will be quite fast for reading many files, possible repeatedly.

Then there is readline , which is a useful way to only read in individual lines, in incremental amounts at a time, and return them as strings. The last explicit method, readlines , will read all the lines of a file and return them as a list of strings.

Note : For the remainder of this article we will be working with the text of the book The "Iliad of Homer", which can be found at gutenberg. Let's start off with the the readline method, which reads a single line, which will require us to use a counter and increment it:.

This code snippet opens a file object whose reference is stored in fp , then reads in a line one at a time by calling readline on that file object iteratively in a while loop.

It then simply prints the line to the console. Though, this approach is crude and explicit. Most certainly not very Pythonic. We can utilize the readlines method to make this code much more succinct. The readlines method reads all the lines and stores them into a List. We can then iterate over that list and using enumerate , make an index for each line for our convenience:. Check out our hands-on, practical guide to learning Git, with best-practices, industry-accepted standards, and included cheat sheet.

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