How Can Python Efficiently Count Lines in Very Large Files?

Efficient Line Counting in Large Files with Python

Determining the line count of massive files is crucial for various applications. While conventional approaches using for loops can be time-consuming and memory-intensive, Python offers an optimized solution.

Concise and Efficient Line Counting

The following code snippet showcases a single-line approach for line counting, outperforming the loop method presented in the question:

num_lines = sum(1 for _ in open('myfile.txt'))

This code leverages Python's generator expression, which iterates over each line in the file, without holding all lines in memory. The sum(1 for _ in ...) construction counts the number of lines.

Performance Enhancements

For further speed optimization and increased robustness, consider the following enhancements:

• Read in binary mode: rb mode ensures efficient reading of binary data from the file.
• Utilize a with block: The with block automatically closes the file handle, ensuring proper cleanup.

An updated code snippet with these enhancements:

with open("myfile.txt", "rb") as f:
    num_lines = sum(1 for _ in f)

Note

For the deprecated rbU mode in Python 3.3 and later, use rb instead. This mode is removed in Python 3.11.

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