Emacs specific region read only

How does one make a specific region in a text file read only when using emacs. I know ctrl+X+Q to make the whole file a read only.

I am currently writing a 开发者_如何学Pythoncode and I do not want to modify by accident the first 40 lines of my code while working on lines 41 and upwards.

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Use text properties:

(defun set-region-read-only (begin end)
  (interactive "r")
  (add-text-properties begin end '(read-only t)))

Relevant Docs:

Text-Properties

Changing Properties

Special Properties (like read-only)

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You can use narrow-to-region (C-x n n) to narrow the buffer just to the part you want to change. Then you won't see or be able to change the region you don't want to change.

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You can also apply highlight-changes-mode. That way you can see which text is changed as it is in different color. narrow-to-region is a good solution. You can also use that with 2 buffer, so you can see the read-only text too, if needed.