✍️ Writing Files

Writing files lets your program save results and create logs, reports, exports, and more.

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✅ File Modes

Mode	Meaning	Notes
"w"	write (overwrite)	creates file if missing
"a"	append	writes at end, creates if missing
"x"	create exclusively	fails if file exists
"r+"	read/write	file must exist

For binary data use "wb" / "ab".

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✅ Basic Pattern

with open("output.txt", "w", encoding="utf-8") as f:
    f.write("Hello!\n")

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⚠️ Newlines on Windows

Python will translate "\n" to the platform newline automatically for text files. For CSV, Python recommends newline='' when opening the file (covered in the CSV lesson).

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🔍 Key Takeaways

• "w" overwrites; "a" appends.
• Use with so buffers flush and the file closes.
• Prefer explicit UTF-8 encoding for text.

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