Python Program to Get Line Count of a File

Python, a general-purpose language with a clean syntax, is a great tool for automating tasks like counting the number of lines in a file. This is useful when you need to analyze large text files, data logs, or code bases. In this article, we will discuss how to create a Python program that can count the number of lines in a file.

Before we start, ensure that you have Python installed on your computer. As of my knowledge inn July 2023, the most recent stable version of Python is 3.11. However, any version after Python 3 should work fine for our purposes.

Advertisement

Approach

Our approach to count the number of lines in a file using Python is quite straightforward. We will:

1. Open the file in read mode.
2. Use the built-in `readlines()` function to read all the lines from the file.
3. Use the `len()` function to count the number of lines.

Python Program to Get Line Count of a File

Here’s a simple Python program that demonstrates the above approach:

In this program, the function `count_lines` opens the file whose name is passed as the parameter `filename`. The `with` statement is used here to ensure that the file is properly closed after it is no longer needed. The `readlines()` function is called on the file object, which returns a list where each element is a line in the file. We then return the length of this list, which represents the number of lines in the file.

You would need to replace ‘myfile.txt’ with the name of the file you want to count lines from. Also, this program assumes that the file is located in the same directory as the Python script. If the file is located in a different directory, you would need to specify the full path to the file.

Improved Version: Large Files

The previous version works fine for small to moderately-sized files. However, if you are dealing with very large files, that approach can be memory-inefficient because it reads the entire file into memory at once. Here’s an improved version that reads the file line by line, which is more suitable for large files:

This version uses a `for` loop to iterate over each line in the file, incrementing a counter at each iteration. This way, only one line is held in memory at a time, making this program capable of handling files that are gigabytes in size.

Conclusion

Python makes it easy to read and manipulate files, and with just a few lines of code, you can count the number of lines in a file. Whether you’re dealing with small text files or large datasets, Python’s built-in functions and efficient memory management make it an excellent choice for such tasks.