How Can I Efficiently Insert Text into the Middle of a Text File in Python?

Modifying Text Files in Python

When working with text files using Python, it is essential to understand the limitations of file manipulation. While it is possible to append to a file or overwrite specific sections using the seek method, inserting text into the middle of a file without rewriting it is not feasible.

This restriction on text file modification is due to the nature of the file system. When you modify a file, the system cannot simply "insert" text in the middle without disrupting the existing data. Instead, the entire file must be read, modified, and then rewritten.

In Python, a common approach to modifying text files is to read the original content, make the necessary changes, and write the modified data to a new file. Once the new file is complete, it can be renamed to replace the original file. This approach ensures that the original file remains intact in case the modification process fails.

To illustrate this method, here is a Python script that inserts a string into a text file:

import os

# Read the original file
with open('myfile.txt', 'r') as f:
    file_content = f.read()

# Insert the string at the desired position
insert_position = 10  # Example position
new_content = file_content[:insert_position] + 'Inserted string' + file_content[insert_position:]

# Write the modified content to a new file
with open('new_file.txt', 'w') as f:
    f.write(new_content)

# Rename the new file to replace the original
os.rename('new_file.txt', 'myfile.txt')

By following these steps, you can effectively insert text into a text file without re-writing the entire contents.

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