flask bank restful api

BANK rest api

# flask , flask_restful, pymongo, bcrypt library
from flask import Flask, jsonify, request
from flask_restful import Api, Resource
from pymongo import MongoClient
import bcrypt

# Create Flask object
# Create flask_restful object with Flask object input
app = Flask(__name__)
api = Api(app)

# Create MongoClient object
# Create new mongo db MoneyManagementDB
# Create new collections users
client = MongoClient("mongodb://db:27017")
db = client.MoneyManagementDB
users = db["Users"]

# Create Register resource
class Register(Resource):

    # post method
    def post(self):
        # from flask request.get_json()
        #Step 1 is to get posted data by the user
        postedData = request.get_json()

        #Get the data
        username = postedData["username"]
        password = postedData["password"] #"123xyz"

        # if user doesn't exist in db, 301 status returns
        if UserExist(username):
            retJson = {
                'status':301,
                'msg': 'Invalid Username'
            }
            return jsonify(retJson)

        # password encrypted
        hashed_pw = bcrypt.hashpw(password.encode('utf8'), bcrypt.gensalt())

        # user collections inserts the new person in users collections
        #Store username and pw into the database
        users.insert({
            "Username": username,
            "Password": hashed_pw,
            "Own":0,
            "Debt":0
        })

        retJson = {
            "status": 200,
            "msg": "You successfully signed up for the API"
        }
        return jsonify(retJson)

# return debt from user['Username'][0]['Debt']
def debtWithUser(username):
    debt = users.find({
        "Username":username
    })[0]["Debt"]
    return debt

def generateReturnDictionary(status, msg):
    retJson = {
        "status": status,
        "msg": msg
    }
    return retJson
# mongodb collection_name.update method
# update mongo db Own field in user collections
def updateAccount(username, balance):
    users.update({
        "Username": username
    },{
        "$set":{
            "Own": balance
        }
    })

def updateDebt(username, balance):
    users.update({
        "Username": username
    },{
        "$set":{
            "Debt": balance
        }
    })

api.add_resource(Register, '/register')
api.add_resource(Add, '/add')
api.add_resource(Transfer, '/transfer')
api.add_resource(Balance, '/balance')
api.add_resource(TakeLoan, '/takeloan')
api.add_resource(PayLoan, '/payloan')


if __name__=="__main__":
    app.run(host='0.0.0.0')

docker yml file

version: '3'
services:
  web:
    build: ./web
    ports:
      - "5000:5000"
    links:
      - db
  db:
    build: ./db