Python: AttributeError: module 'core' has no attribute 'children'-CodePudding

Hello I'm working on mobile application with kivy and python. Everything was fine until I wanted to use sqlite3. Here is my directory structure:

application
├───main.py
├───core
│   └───__pycache__
|   ├───calendar_screen.py
|   ├───children.py
|   ├───menu.py
|   ├───screen_manager.py
|   ├───settings.py
|   └───vaccination.py
├───database
|   ├───vaccination_calendar.db
|   ├───vaccination_calendar.py
│   └───__pycache__
├───fonts
│   └───static
│       ├───OpenSans
│       ├───OpenSans_Condensed
│       └───OpenSans_SemiCondensed
├───images
│   └───icons
├───layouts
|   ├───calendar.kv
|   ├───children.kv
|   ├───menu.kv
|   ├───screen_manager.kv
|   ├───settings.kv
|   └───vaccination.kv
└───__pycache__

Relevent code main.py

from kivymd.app import MDApp

from core.screen_manager import WindowManager


class VaccinationCalendarApp(MDApp):
    def build(self):
        self.theme_cls.primary_palette = "Green"
        return WindowManager()


if __name__ == "__main__":
    VaccinationCalendarApp().run()

screen_manager.py

from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager

Builder.load_file("layouts/screen_manager.kv")


class WindowManager(ScreenManager):
    pass

screen_manager.kv

#: import Menu core.menu
#: import Calendar core.calendar_screen
#: import Children core.children
#: import Vaccination core.vaccination
#: import Settings core.settings

<WindowManager>:
    Menu:
    Calendar:
    Children:
    Vaccination:
    SettingsScreen:

children.py

from kivy.lang import Builder
from kivy.uix.screenmanager import Screen
from kivymd.uix.list import OneLineAvatarIconListItem, IconLeftWidget
from application.database.vaccination_calendar import get_children

Builder.load_file("layouts/children.kv")

class Children(Screen):
    pass

vaccination_calendar.py

import sqlite3

def get_children():
    statement = "select * from children"

    with sqlite3.connect("vaccination_calendar.db") as conn:
        cursor = conn.cursor()
        cursor.execute(statement)
        children_list = [{"id": child[0], "name": child[1], "birth_date": child[2], "days_age": child[3]}
                         for child in cursor.fetchall()]
        conn.commit()

    return children_list

Everything was fine until this line in children.py: from application.database.vaccination_calendar import get_children. After adding this line I get AttributeError with traceback:

Traceback (most recent call last):
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\application\main.py", line 3, in <module>
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\builder.py", line 305, in load_file
     return self.load_string(data, **kwargs)
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\builder.py", line 372, in load_string
     parser = Parser(content=string, filename=fn)
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\parser.py", line 483, in __init__
     self.parse(content)
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\parser.py", line 590, in parse
     self.execute_directives()
   File "C:\Users\przem\PycharmProjects\vaccination_calendar\env\lib\site-packages\kivy\lang\parser.py", line 559, in execute_directives
     mod = getattr(mod, part)
 AttributeError: module 'core' has no attribute 'children'

I suspect that it is something wrong with circular dependency but tbh i can't see anything wrong with this. File i past here are in imported order starting from main.py Any idea what is wrong?

I tried to import vaccination_calendar.py by method in children.py but after that i get ModuleNotFoundError I also tried to import in to main.py and there it works but then i don't see any idea to use vaccination_calendar.py in children screen.

CodePudding user response：

The error can be found in the following line:

from application.database.vaccination_calendar import get_children

I assume you run main.py. When you do so ./application gets added to sys.path. That is why Python will never be able to resolve a module path like application.some.module_path, instead it should only be the some.module_path part.

The error message is pretty cryptic, but that is the result of Kivy trying to parse the screen_manager.kv file. In the process of doing so it finds this wrong import and raises an error deep inside the Kivy library (cause it tries to parse a .kv file) instead of directly telling you what exactly is wrong.

CodePudding user response：

I find a solution to this problem. I don't know where exactly was the problem but I change the way I import vaccination_calendar. I change this:

from application.database.vaccination_calendar import get_children

To this:

sys.path.append('database')

import vaccination_calendar

Pycharm still see a problem but it works for me. Maybe someone can use it.