How Can I Edit a Text File In-Place Efficiently?

Editing a Text File In-Place: A Comprehensive Guide

Introduction

Editing a text file in-place provides a versatile approach to modifying its contents without creating a separate duplicate. By understanding the available techniques, you can quickly perform search-and-replace operations efficiently.

Search and Replace Using fileinput

The fileinput module offers a convenient solution for modifying files in-place. By redirecting the standard output to the original file, any print statements within the loop will write back to it.

import fileinput

for line in fileinput.input("test.txt", inplace=True):
    print('{} {}'.format(fileinput.filelineno(), line), end='')

Explicit File Manipulation

For more comprehensive code, consider explicitly manipulating the file:

Option 1: Reading and Writing the Entire File

If the file size permits, you can read the entire file into memory, modify it, and write it back in writing mode.

Option 2: Using a Temporary File for Large Files

For larger files, it's practical to use a temporary file to avoid potential memory issues. By moving the original file to a temporary one, you can process it line by line and write back to the original file.

Conclusion

Understanding the available techniques for in-place file editing empowers you to implement search-and-replace operations effectively. Whether you choose fileinput for quick operations or explicit file manipulation for larger files, selecting the appropriate method ensures efficient and reliable results.

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