File Reading and Writing

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

This is useful when you want to save data to a file or load data from one.

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 use a with block to handle this automatically.

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

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

• with ensures the file is closed automatically.
• file.read() loads the entire file as a string.

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

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

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

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

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

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