How to solve psycopg2.errors.UndefinedColumn: column "beans" does not exist?

Question

I am trying to send a get request to a backend route that returns some query results based on the parameters that are sent through the get request. At first I just used hardcoded values for my parameters that were passed to the backend route and the queries returned accurate results but when I replace those hardcoded parameters with the username that is a stateful object, it somehow reads the %s value as the column instead of the column name.

My get request looks like this:

async function getStatsData(username) {
    const user = username;
    const flashcard_id = 1;
    const req = axios.get(`http://127.0.0.1:5000/stat/${user}/${flashcard_id}`)
    const res = await req;
    return res.data.results.map((statsItem, index) => {
        return {
            stat1: statsItem.stat1,
            stat2: statsItem.stat2,
            stat3: statsItem.stat3,
            stat4: statsItem.user,
            key: statsItem.key,
            flashcard_id: statsItem.flashcard_id
        }
    })
}

and my backend route looks like this:

@app.route('/stat/<user>/<flashcard_id>', methods=['GET', 'POST', 'OPTIONS'])
def stats(user, flashcard_id):
  def get_total_percent_correct(username):
    correct = d.db_query('SELECT COUNT(*) FROM cards.responses WHERE guess = answer AND username = %s' % username)[0][0]
    total = d.db_query('SELECT COUNT(*) FROM cards.responses WHERE username = %s' % username)[0][0]
    try:
        return round(float(correct)/float(total),3)*100
    except:
        print('0')

  def get_percent_correct_for_flashcard(username,flashcard_id):
    total = d.db_query('SELECT COUNT(*) FROM cards.responses WHERE username = %s AND flashcard_id = %s' % (username, flashcard_id))[0][0]
    correct = d.db_query('SELECT COUNT(*) FROM cards.responses WHERE flashcard_id = %s AND guess = answer AND username = %s' % (flashcard_id, username))[0][0]
    try:
        return round(float(correct)/float(total),3)*100
    except:
        print('0')

  def get_stats_for_flashcard(username, flashcard_id):
    attempts = d.db_query('SELECT COUNT(*) FROM cards.responses WHERE username = %s AND flashcard_id = %s' % (username, flashcard_id))[0][0]
    correct = d.db_query('SELECT COUNT(*) FROM cards.responses WHERE flashcard_id = %s AND guess = answer AND username = %s' % (flashcard_id, username))[0][0]
    missed = attempts - correct
    return attempts, correct, missed
  
  data = [{
    'flashcard_id': flashcard_id,
    'user': user,
    'stat1': get_total_percent_correct(user),
    'stat2': get_percent_correct_for_flashcard(user, flashcard_id),
    'stat3': get_stats_for_flashcard(user, flashcard_id),
    'stat4': 'nothing yet',
    'key':999
  }]

  return {"response_code" : 200, "results" : data}

The error is insided the function get_total_percent_correct. here is the full error message:

 File "/home/bryant/work/memorylearning/my-app/backend/main.py", line 66, in get_total_percent_correct
    correct = d.db_query('SELECT COUNT(*) FROM cards.responses WHERE guess = answer AND username = %s' % username)[0][0]
  File "/home/bryant/work/memorylearning/my-app/backend/main.py", line 17, in db_query
    self.cursor.execute(q)
psycopg2.errors.UndefinedColumn: column "beans" does not exist
LINE 1: ...OM cards.responses WHERE guess = answer AND username = beans

I appreciate any help. Thanks for your time