Python Write and Append to Text Files

This guide explains write and append to text files through a focused Python example. You will learn the behavior to expect, why it matters in a real program, and how to recognize the common mistakes before applying it in your own project.

What You Will Learn

Writing replaces content in w mode; appending adds text to the end in a mode. Use explicit encoding and deliberate newline characters to make output predictable.

When and Why to Use It

The following example focuses on a practical use of Write and Append to Text Files.

Step-by-Step Example

from pathlib import Path
from tempfile import TemporaryDirectory

with TemporaryDirectory() as directory:
    log_path = Path(directory) / "events.txt"
    log_path.write_text("Started\n", encoding="utf-8")
    with log_path.open("a", encoding="utf-8") as log_file:
        log_file.write("Finished\n")
    print(log_path.read_text(encoding="utf-8"))

Understanding the Example

The file contains both event lines because the second operation uses append rather than overwrite.

Expected Output

Started
Finished

Important Behavior and Edge Cases

Do not expect print to a file to behave like an append unless you explicitly open the file in append mode or pass file=.

Try It Yourself

Create a journal file and append two timestamps.

For file examples, use a dedicated practice directory or a temporary directory. Make sure you understand whether a call reads, creates, overwrites or appends before using it on important files.

Common Beginner Mistakes

• Do not expect print to a file to behave like an append unless you explicitly open the file in append mode or pass file=.
• Assuming the current working directory, encoding, filesystem contents or file permissions will be identical on every computer.
• Skipping the practice step and assuming the example covers every input. Test at least one normal case and one edge case relevant to this topic.

Key Takeaways

• Writing replaces content in w mode; appending adds text to the end in a mode.
• The file contains both event lines because the second operation uses append rather than overwrite.
• Apply the technique deliberately, checking its documented input requirements and failure behavior before integrating it into a larger project.