Sentence in text is read only even though the buffer is not, how to fix this?

Question

I am running emacs 24 with the Inferior Python mode for the interpreter. See below for all the minor modes in effect. Basically the problem is that particular lines (say at the prompt) remain read-only even when I mark toggle "read-only-mode" and I can edit the rest of the buffer.

I am not able to figure out why this might be happening. I have tried toggle-read-only as well. It seems like something related with the font-lock or something else since the behavior happens only at the python prompt lines.

The buffer is running the following minor-modes.

Enabled minor modes: Auto-Composition Auto-Compression Auto-Encryption     
Column-Number Compilation-Shell Diff-Auto-Refine Electric-Indent           
Electric-Pair File-Name-Shadow Font-Lock Global-Company Global-Ede         
Global-Eldoc Global-Font-Lock Global-Semantic-Decoration                   
Global-Semantic-Highlight-Func Global-Semantic-Idle-Completions            
Global-Semantic-Idle-Scheduler Global-Semantic-Idle-Summary                
Global-Semantic-Mru-Bookmark Global-Semantic-Show-Unmatched-Syntax         
Global-Semanticdb Ido-Everywhere Line-Number Mouse-Wheel Recentf           
Semantic Shell-Dirtrack Tooltip Winner                                     

Answer 1

You can use the following commands to set the read-only text property for the marked region. The code is based on https://stackoverflow.com/questions/7410125

(defun set-region-read-only (begin end)
  "Sets the read-only text property on the marked region.

Use `set-region-writeable' to remove this property."
  ;; See https://stackoverflow.com/questions/7410125
  (interactive "r")
  (with-silent-modifications
    (put-text-property begin end 'read-only t)))

(defun set-region-writeable (begin end)
  "Removes the read-only text property from the marked region.

Use `set-region-read-only' to set this property."
  ;; See https://stackoverflow.com/questions/7410125
  (interactive "r")
  (with-silent-modifications
    (remove-text-properties begin end '(read-only t))))

Answer 2

That zone of text probably has a non-nil value for text property read-only.

Commands such as read-only-mode (and toggle-read-only) have no effect on this, as their doc tells you. C-h f read-only-mode says:

Also, note that this command works by setting the variable buffer-read-only, which does not affect read-only regions caused by text properties. To ignore read-only status in a Lisp program (whether due to text properties or buffer state), bind `inhibit-read-only' temporarily to a non-nil value.

To see the text properties at a given position, use C-u C-x = at that position.

To be able to tell you just what you might want to do in your context, let us know what you are really trying to do, which might include why. Are you doing something by program (Lisp)? If so, what? Or are you trying to do something only interactively? If so, what?