Python import - Module not found

Question

I am following a Flask tutorial (on Pluralsight). I have come to where I need to initialize a database, using Flask-SQLalchemy. In the tutorial this is done via the following command, inside Python:

from PyBook.PyBook import db
from PyBook.PyBook.Models import Company

(Actually the names are different in the tutorial, but the concept is very much the same)

However, when I try to run the commands above, I get an error:

Traceback (most recent call last): 
File <stdin>, line 1, in <module> 
File  "C:\Users\Jakob-Desktop\source\repos\PyBook\PyBook\PyBook.py", line 3, in <module
from forms.add_company import AddCompanyForm 
ModuleNotFoundError: No module named 'forms'

Which suggests that the error is in either PyBook.py or add_company (which is referenced by PyBook, as you can see below).

Can anyone tell me what I am missing? I am kind of new to Python.

PyBook.py

from flask import Flask, render_template, url_for, flash, redirect, request
from flask_sqlalchemy import SQLAlchemy
from forms.add_company import AddCompanyForm
import secrets, os

app = Flask(__name__)
app.config['SECRET_KEY'] = secrets.token_urlsafe(16)

basedir = os.path.abspath(os.path.dirname(__file__))
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqllite:///' + os.path.join(basedir, 'pybook.db')
db = SQLAlchemy(app)

@app.route('/')
@app.route('/index')
def index():
    return render_template('index.html')

(...)

add_company.py

from flask_wtf import Form
from wtforms.fields import StringField
from wtforms.fields.html5 import URLField
from wtforms.validators import DataRequired, url

class AddCompanyForm(Form):
    name = StringField('name', validators=[DataRequired()])

Update

As far as I can tell, the folder structure is correct:

Answer 1

Use from .forms.add_company import AddCompanyForm as a '.' is used to go through the current directory.

Answer 2

The issue is that the 'forms' folder is not in the PYTHONPATH. If you ever want to look at what is in the PYTHONPATH, you could use:

import sys

print(sys.path)

You need to add a file (usually empty but not always) called __init__.py in the forms folder. I normally would also add one in the main PyBook folder.

Here is a great guide to understanding how imports work:

Definite Guide To Python Imports

Alternatively, you could also add this to the top of your code in PyBook.py

import sys
import os

sys.path.append(os.path.join(os.path.abspath(os.path.dirname(__file__)), 'forms'))

If you were to add the code, you won't have to do something like:

from forms.add_company import AddCompanyForm

but you could just use:

from add_company import AddCompanyForm