How to Append Data to an Existing File using Python

To append data to an existing file using Python:

# The new data to be appended
new_data = " This is the additional data to be added to the file"

# File path, including the r letter before the path to avoid unicode errors
file_path = r"path to file\file_name.file_extension"

# Opening the file in append mode and writing the data
with open(file_path, "a") as file:
    file.write(new_data)

Example of Appending Data to an Existing File using Python

(1) Assuming an existing text file called “output“.

The file is currently stored in a folder called “Test“, where the full path of the file is:

The text file currently contains the following information:

The ultimate goal is to append the following new data at the end of the file without erasing its contents:

(2) The following Python script can then be used to append the data at the end of the file:

# The new data to be appended
new_data = " Join our community of learners by subscribing to our channel."

# File path, including the r letter before the path to avoid unicode errors
file_path = r"C:\Users\Ron\Desktop\Test\output.txt"

# Opening the file in append mode and writing the data
with open(file_path, "a") as file:
    file.write(new_data)

Notice that there is a space before the first letter of the new_data string. This is to ensure there is a space between the last sentence that is currently in the text file, and the beginning of the new appended sentence.

If you run the script (adjusted to your file_path), you’ll see the following content of the text file after appending the data, where the appended portion is highlighted in green:

(3) What if you want to append the data in a new line?

In that case, simply add “\n” at the beginning of the new data that you wish to add:

# The new data to be appended
new_data = "\nJoin our community of learners by subscribing to our channel."

# File path, including the r letter before the path to avoid unicode errors
file_path = r"C:\Users\Ron\Desktop\Test\output.txt"

# Opening the file in append mode and writing the data
with open(file_path, "a") as file:
    file.write(new_data)

The resulted text file: