File Reading and Writing

Python allows you to read from and write to text files using the built-in open() function.

This is useful for saving data to a file or loading it back later.

Use open(filename, mode) to work with a file.

• "r" = read (default)
• "w" = write (overwrites file)
• "a" = append (adds to the end)
• "x" = create (fails if file already exists)

Always close a file after using it — or better yet, use a with block to handle this automatically.

Open a file in "r" mode to read its contents.

Copy
with open("greeting.txt", "r") as file:
    content = file.read()
    print(content)

• The with statement ensures the file closes automatically.
• The read() method loads the entire file into a single string.

Open a file in "w" mode to create or overwrite it.

Copy
with open("note.txt", "w") as file:
    file.write("This is a new line.")

• The "w" mode creates the file or replaces its content.
• Use the write() method to add text to the file.

Open a file in "a" mode to add new content without removing existing data.

Copy
with open("note.txt", "a") as file:
    file.write("\nThis line is added.")

• The "a" mode preserves existing content and writes new text at the end.