Flask-Sqlalchemy data mutation when replacing text - python-3.x

Question

I'm using flask-sqlalchemy on a site to save some information from a textarea. This text area could contain some simple bbcode that I would handle later to allow text formatting.
When I save or update anything, everything looks normal before and after the update operation. When I go to edit that same information, it has <br>, <strong> and other tags that have been placed in the text. Is this something that flask-sqlalchemy does? If so, how do I disable this? It seems like the problem is in flask-sqlchemy based on where the problem happens, and I'd rather handle any formatting myself.
I've also checked how the data is stored in the database. The database contains the HTML code rather than the bbcode markup, so the problem does not lie in the templates that display the editing view.
EXAMPLE
In the form, I submit this data.
[b]hello world[/b]
how are you
In the flask route for the update, I print out the data
#app.route("/update/item/<id>", methods=['POST']
def update(id):
# While testing I'm not going to bother with escaping anything.
# Once I figure out what's causing this, I'll do so with the escape() function.
item = request.form['item']
print(repr(item)) # "[b]Hello World[/b]\r\n\r\nhow are you"
Item.query.filter_by(id=id).update(dict(item=str(item))
queried = Item.query.filter_by(id=id).first()
print(queried.item) # "[b]Hello World[/b]\r\n\r\nhow are you"
When i go to edit the item, it displays this in the text area
<strong>Hello World</strong>
<br>
<br>how are you
rather than
[b]Hello World[/b]
how are you
UPDATE:
This only appears to happen when the following code is ran
#...
def paginate(page):
items = Item.query.order_by(Item.id.desc()).paginate(page=page, per_page=10)
for text in items:
# Just replacing [b] and [/b] as an example here. I'll have everything
# regexed out and replaced in a dedicated function.
# This replacing appears to be the culprit. Commenting this out fixes it.
text.item = text.item.replace("[b]", "\<strong\>")
text.item = text.item.replace("[/b]", "\</strong\>")
return items

Answer 1

This problem was brought about by not knowing that sqlalchemy automatically saves changes back to the database when an attribute is changed, for example, by parsing the bbcode for later use. While I may have strong opinions on mutable data structures automatically saving themselves (it should NEVER happen), here's how to fix this if anyone else has the same problem.
First, know that sqlalchemy will automatically save if you modify anything on your sql query unless you detach it from the database, EVEN IF you use autoflush=False and autocommit=False (I tried both). Before making any changes, call the expunge() function and then make your changes. This detaches the query from the database and allows you to modify to your heart's content without any (potentially devastating) data mutation happening in your database.
In my case, this means my paginate function should look like this
# Make sure you have your db object imported somewhere above
def paginate(page):
items = Item.query.order_by(Item.id.desc()).paginate(page=page, per_page=10)
for text in items:
db.session.expunge(text)
text.item = text.item.replace("[b]", "<strong>")
text.item = text.item.replace("[/b]", "</strong>")
return items