CODEWITHSUNDEEP
pythonjsonpython-3.xflaskjinja2
Pascal
Pascal

Reputation: 1751

How to return a Python Object via Jinja2 back to Python?

Couldn't find any question related to this issue. I'm probably doing it the wrong way because I'm sure there must be an easier way to achieve this, but I couldn't figure it out yet.

--> I'm trying to get a Python object from Jinja2 back to Python, so I can access its values back in Python.

So I'm passing an array of users from Python(Flask) to a drop-down in HTML which looks like this:

<div class="form-group">
    <label>User:</label>
    <select class="form-control" name="user">
        {% for user in users %}
            <option value="{{ user }}">{{ user.firstname }} {{ user.lastname }} 
            ({{ user.birthdate }})</option>
        {% endfor %}
    </select>
</div>

This works perfectly and I can select a user in the dropdown. Now I want to access the users user.address attributes back in Python. (of course these attributes are already defined in the user class).

So I have a function like this in Python (Flask) which gets triggered when pressing a button:

@app.route("/display_user", methods=["POST"])
def display_user():

    user = request.form["user"] 
    address = user.address
    return render_template("show.html", address=address)

Now I'm getting the following error:

"AttributeError: 'str' object has no attribute 'address'".

I'm getting back the json as a string which looks like this:

{'firstname': 'test','lastname': 'test','birthday': 'test','address': 'test'}

I should now probably create a dict out of this string/json and then access these values with ['address'], but somehow I couldn't figure out how. I tried it with json.dumps() which did not work, still the same error message. Also I figured there must be an easier/better way to achieve this.

Any suggestions? (using Python 3.6.2)

Upvotes: 0

Views: 1007

Answers (2)

Pascal
Pascal

Reputation: 1751

ok, so I ended up with this solution:

I only returned the ._id and not the whole instance of the user as follows:

Jinja2/HTML:

<option value="{{ user._id }}">{{ user.firstname }} {{ user.lastname}} ({{ user.birthdate }})</option>

Then I just did a new query for the user in my database (I'm using MongoDB) using its _id.

Python 3.6:

user_id = request.form["user"]
user = User.get_by_id(user_id)

And then I could access it's attributes with user.address and so on. Works fine, but I'm not quite happy with the solution since I need to query the database again.

So if anyone has a different approach, I'm glad to hear it :-)

Upvotes: 1

Peter234
Peter234

Reputation: 1052

If you get back json as a string you can use json.loads.

import json
values = json.loads('{"firstname": "test","lastname": "test","birthday": "test","address": "test"}')
print(values["firstname"])

This will output test. Please note that the string you posted is not Json. JSON strings must use double quotes.

Upvotes: 0

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