Writing to Files in Python

Writing to Files in Python

In Python, writing to files is an essential skill. You can either append content to an existing file or overwrite its contents. This post will guide you through the different methods of writing to files using the built-in open() function.

Writing to an Existing File

To write to an existing file, you need to specify a mode in the open() function:

  • "a" - Append: Adds content to the end of the file.
  • "w" - Write: Overwrites any existing content.

Example: Append Content to a File

Open the file example_append.txt and append content:

file = open("example_append.txt", "a")
file.write("Now the file has additional content!")
file.close()

To read the updated content:

file = open("example_append.txt", "r")
print(file.read())

Example: Overwrite Content in a File

Open the file example_overwrite.txt and overwrite its content:

file = open("example_overwrite.txt", "w")
file.write("Oops! The original content has been deleted!")
file.close()

To verify the change:

file = open("example_overwrite.txt", "r")
print(file.read())

Note: The w mode will completely overwrite the file's existing content.

Creating a New File

When creating a new file, you can use the following modes:

  • "x" - Create: Creates a new file but raises an error if the file already exists.
  • "a" - Append: Creates a new file if it does not exist.
  • "w" - Write: Creates a new file if it does not exist.

Example: Create a New File

Create a new file called my_new_file.txt:

file = open("my_new_file.txt", "x")

To create a file if it does not exist:

file = open("my_new_file.txt", "w")

Exercise

What happens to the original file content if you open a file like this:

file = open('example_overwrite.txt', 'w')
  • The original content will be overwritten.
  • Any new content will be added after the original content.

Conclusion

Understanding how to write to files is crucial for data manipulation in Python. Whether you’re appending new data or overwriting existing content, the open() function provides a straightforward way to manage file operations. Always be cautious with the w mode, as it will replace any existing data.