How to store data from python/kivy app - mysql

Question

I'd like to know how to store data from my app so I can review the data when I re-run the app.
e.g. I type some info in a TextInput and then when I click the submit button, the info is pasted in a label, so I close the app and when I reopen it the info should be appearing in the label. I know that there are sqlite3 and mysql but I don't know how to apply it into my python/kivy code.
Please anyone suggest me how that can be done.
If possible show with an example, it would be perfect.
Thanks in advance,
My py code:
from kivy.app import App
from kivy.uix.screenmanager import ScreenManager, Screen
from kivy.lang import Builder
from random import shuffle
from kivy.core.window import Window
Window.clearcolor = [1, 1, 1, 1]
Window.size = (550, 650)
Builder.load_file('builder.kv')
class MainScreen(ScreenManager):
pass
class Menu(Screen):
pass
class Levels(Screen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
def on_pre_enter(self):
Window.bind(on_keyboard=self.voltar)
def voltar(self, window, key, *args):
if key == 27:
App.get_running_app().root.current = 'menu'
return True
def on_pre_leave(self):
Window.unbind(on_keyboard=self.voltar)
class LvLogos(Screen):
def on_pre_enter(self):
Window.bind(on_keyboard=self.voltar)
def voltar(self, window, key, *args):
if key == 27:
App.get_running_app().root.current = 'menu'
return True
def on_pre_leave(self):
Window.unbind(on_keyboard=self.voltar)
class Logo(Screen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
def shuffle(self):
letter = self.letters
self.s = shuffle(letter)
return letter
def on_pre_enter(self):
Window.bind(on_keyboard=self.voltar)
def voltar(self, window, key, *args):
if key == 27:
App.get_running_app().root.current = 'menu'
return True
def on_pre_leave(self):
Window.unbind(on_keyboard=self.voltar)
class LvShields(Screen):
pass
class Shield(Screen):
def __init__(self, **kwargs):
super().__init__(**kwargs)
def shuffle(self):
letter = self.letters
self.s = shuffle(letter)
return letter
class QuizZApp(App):
def build(self):
self.icon = 'C:\\Users\\gusta\\PycharmProjects\\QuizzApp\\Images\\QuizzLogo.png'
return MainScreen()
if __name__ == '__main__':
QuizZApp().run()

Answer 1

Of course you can use sqlite3, but the simplest way to store basic data for kivy app like your exaple would be to use json file with kivy's own JsonStore class.
It has the benefit of allocating your file in the right place depending on the platform it is deployed on, you won't need to care where exactly.
Here is a simple example using get(), put() and exists() methods to store typed text from TextInput and load it on a Label. (You won't need to create the file itself, just initialize the object and write (put()) in it).
from kivy.uix.boxlayout import BoxLayout
from kivy.storage.jsonstore import JsonStore
from kivy.base import runTouchApp
from kivy.lang import Builder
from kivy.properties import ObjectProperty
kv='''
RootWidget:
orientation: 'vertical'
BoxLayout:
TextInput:
id: txtinpt
Label:
id: lbl
text: root.stored_data.get('mydata')['text'] if root.stored_data.exists('mydata') else ''
Button:
size_hint_y: .3
text: 'Submit'
on_press:
root.stored_data.put('mydata', text=txtinpt.text)
lbl.text = txtinpt.text
'''
class RootWidget(BoxLayout):
stored_data = ObjectProperty(None)
def __init__(self, *args, **kwargs):
super(BoxLayout, self).__init__(*args, **kwargs)
self.stored_data = JsonStore('data.json')
runTouchApp(Builder.load_string(kv))
If you are new to Json, it is a file containing list of pairs, which's value by its own may be a new list of pair. pretty much like python's dict.
For kivy's JsonStore class, it assume you are working with a minimum of two levels, hence {"mydata": {"text": "What you have written last run"}}. It doesn't make much sense in this simple example to have a nested dict, but in general it will be exactly what you want for real applications, like if you wanted to take contacts data for multiple contacts, or you want to store various configurations for multiple widget for the app itself (in this case you may want to read (get()) the data prior of loading the widgets, probably in the App-class's build() method).
reference: https://kivy.org/docs/api-kivy.storage.html