I'm trying to create a simple API and server with MongoDB and Flask in python(pycharm). I'm testing the methods with Postman and so far the GET and DELETE methods work. I'm having troubles with the POST method mainly(for adding an entity). I have 2 classes

repository class

class ExercisesRepository: def __init__(self): self.client = MongoClient('localhost', 27017) self.client.drop_database("exercise_database") # clear everything that was before self.db = self.client.exercise_database # create database self.exercises = self.db.exercises # create table in the database def get_all(self): return [{ 'id': str(exercise['_id']), 'type': exercise['type'], 'calories': exercise['calories'] } for exercise in self.exercises.find()] def add(self, exercise): exercise = {key: exercise[key] for key in exercise} exercise['calories'] = int(exercise['calories']) #line 24 self.exercises.insert_one(exercise) # automatically generates an ObjectId for the exercise return 200 def update(self, exercise_id, exercise): my_query = {"_id": ObjectId(exercise_id)} new_values = {"$set": {"type": exercise["type"], "calories": exercise["calories"]}} self.exercises.update_one(my_query, new_values) return 200 def delete(self, exercise_id): self.exercises.remove(ObjectId(exercise_id)) return 200 def check_database_content(self): for exercise in self.exercises.find(): pprint.pprint(exercise) 

server class

from ExercisesRepository import ExercisesRepository from flask import Flask from flask import request from flask import jsonify import sys app = Flask(__name__) exerciseRepo = ExercisesRepository() exerciseRepo.add({'type': 'Yoga', 'calories': 500}) exerciseRepo.add({'type': 'Walk', 'calories': 300}) exerciseRepo.add({'type': 'Run', 'calories': 100}) @app.route('/') def hello_world(): return 'Hello World!' @app.route("/exercises", methods=['GET', 'POST']) def exercises(): if request.method == 'GET': return jsonify(exerciseRepo.get_all()) elif request.method == 'POST': print(request.form, file=sys.stderr) return jsonify(exerciseRepo.add(request.form)) #line 31 @app.route('/exercises/<exercise_id>', methods=['PUT', 'DELETE']) def exercises_id(exercise_id): if request.method == 'PUT': print(request.form, file=sys.stderr) return jsonify(exerciseRepo.update(exercise_id, request.form)) elif request.method == 'DELETE': return jsonify(exerciseRepo.delete(exercise_id)) if __name__ == '__main__': app.run() 

When I try to make a POST call in postman with a JSON like this : { "type": "Aerobic", "calories": 500 } I get the following message in postman: 500 Internal Server Error Internal Server Error The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application. and in Pycharm console:

File "server.py", line 31, in exercises return jsonify(exerciseRepo.add(request.form))
server\ExercisesRepository.py", line 24, in add exercise['calories'] = int(exercise['calories']) KeyError: 'calories' 127.0.0.1 - - [05/Jan/2020 13:01:50] "POST /exercises HTTP/1.1" 500 -

I'm pretty new to python and this is my first try to make an api so if you could explain as much as possible it would be very helpful. Thanks!