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Implement Python Read File Line By Line (Guide)

by Fahad Saleem

Implement Python Read File Line By Line (Guide)

One of the major reasons of learning Python is for analyzing and manipulating texts. If you are running a program that has to parse through a huge file, then it is highly recommended to use Python read file function for keeping sufficient speed and memory. Python serves the purpose of high-level programming language. The design philosophy of Python is readability and to express ideas in fewer lines of the code as compared to other programming languages such as C. It supports multiple programming paradigms that include object-oriented, functional programming and Imperative styles. It also possesses dynamic memory management features and has a comprehensive library.

read file line by line

Download Python

You can download packages for the latest version of Python from its official website. It is available for a variety of platforms such as MAC OS X, BeOS, MorphOS, MS-DOS etc.

How to Use Python Read Text File Function

In order to employ Python read file functionality line-by-line, it is best to use While loop as follows.

“fileIN = open(sys.argv[1], “r”)

line = fileIN.readline()

while line:

[some bit of analysis here]

line = fileIN.readline()”

The code inputs file for reading. The first command line of the code is the name of the file to be processed. An object fileIN will be created if the file exists and gets opened successfully. The second line of the code reads the first line of the object file and assigns it to a string variable “line”. Then, based on the constancy of line, the While loop executes. The While loop restarts when “line” gets modified. This process continues forever until there are no more lines in the file to be processed. The program then ends.

When you use Python read from file function in this way, the program doesn’t utilize more data than it is set for processing. Hence, it processes the data that it inputs faster while giving its output incrementally. In this manner, the memory usage of the program is kept low, and the processing speed of the computer is not affected a great deal too. This algorithm is quite important if you are writing a CGI script that uses plenty of instances of itself running at a time.

This tutorial provides you the fundamentals for reading large text files line-by-line using Python. You can get more idea about the Python programming language from its tutorial for beginners.




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