Passing Variable from HTML to Python/Flask

Let me try this again. I want to enter a variable into my HTML form to submit, so far from reading the link here How to display a variable in HTML I've tried the following code, which is inside of main.html

  <form>
      Asset Tag:<br>
      <input type="text" name="Asset Tag"><br>
      <input type="submit" value="Submit">
      <form action="{{ asset_tag }}" method="get">
  </form>

I then have a python script that goes like this,

from flask import Flask, render_template
app = Flask('server')

@app.route('/py')
def server():
    return render_template('main.html')
#API URL
JSS_API = 'https://apiresource.com'

#Pre-Defined username and password
username = 'username'
password = 'password'

#Ask User for the Asset tag
asset_tag = {{ }}

After the asset tag is entered it just searches through a JSON file for match, the rest doesn't matter so much so I didn't include the next piece of the script.

So Flask renders my HTML just fine and I can submit a value but it's not being passed back to the script, which makes sense as I'm doing the opposite of the link I provided, but I just can't not think of how it's done. Any suggestions?

You have a few issues that I've outlined below. Overall though, the frontend is passing the variable to the backend, it's just that the variables are only accessible via the request object from within the route to which the data is passed.

I am not sure why you have a <form> nested within a <form> here, but you'll want to remove the inner one since it's not doing anything.
You want to setup your form to POST the data to your backend when submitted. If you don't specify an action, then it will POST to the same page the same page that you're currently viewing.
```
<form method="POST">
    Asset Tag:<br>
    <input type="text" name="tag"><br>
    <input type="submit" value="Submit">
</form>
```
You need to setup your route to accept a POST request so that it can receive data from the form on your page. See here for more information on HTTP methods.
```
@app.route('/py', methods=['GET', 'POST'])
```

Inside of your route, you'll want to check whether it was a GET request (and load a normal page) or whether it was a POST (form data was sent so we should use it)

from flask import request

@app.route('/py', methods=['GET', 'POST'])
def server():
    if request.method == 'POST':
        # Then get the data from the form
        tag = request.form['tag']

        # Get the username/password associated with this tag
        user, password = tag_lookup(tag)

        # Generate just a boring response
        return 'The credentials for %s are %s and %s' % (tag, user, password) 
        # Or you could have a custom template for displaying the info
        # return render_template('asset_information.html',
        #                        username=user, 
        #                        password=password)

    # Otherwise this was a normal GET request
    else:   
        return render_template('main.html')