Inserting a Line at the Middle of a File in Python

Inserting a line at a specified position in a file while maintaining the integrity of the existing content can be achieved using Python's file handling capabilities.

To insert a line at index x in a file, follow these steps:

1. Open the file for reading.
2. Read the entire file into a list of lines using the readlines() method.
3. Insert the desired line at the specified index using the insert() method.
4. Open the file for writing.
5. Join the list of lines back into a string using join().
6. Write the modified string to the file.

Here's an example code that implements these steps:

with open("path_to_file", "r") as f:
    contents = f.readlines()

# Insert the line at index x
index = 2
value = "Charlie"
contents.insert(index, value)

with open("path_to_file", "w") as f:
    contents = "".join(contents)
    f.write(contents)

This code opens the file, reads its contents into a list contents, inserts the line "Charlie" at line 2 (index 1), then overwrites the file with the modified content.